Menstruation and Menstrual Disorders: Anovulation

Anovulation is the failure of the ovary to release ova over a period of time generally exceeding 3 months. The normal functioning ovary releases one ovum every 25–28 days. This average time between ovulation events is variable, especially during puberty and the perimenopause period.¹ For nonpregnant women aged 16–40 anovulation is considered abnormal and a cause of infertility in 30% of fertility patients.²

One of the cardinal signs of anovulation is irregular or absent menstrual periods. Oligomenorrhea is defined as more than 36 days between menstrual cycles or fewer than eight cycles per year.³ In the absence of pregnancy, menstruation follows ovulation by approximately 14 days. Because menstruation is linked to ovulation, the clinical finding of oligomenorrhea correlates with oligoovulation. This predictable pattern of ovulation and menstruation is regulated by a cyclic change in hormones. Consequently, the diagnosis of ovulation dysfunction includes the assessment of the hormones and systems involved in ovulation and not just the symptom of amenorrhea.

This chapter includes a basic review of the process of ovulation and the primary mechanisms of anovulation. Anovulation is covered using a systems approach. This approach includes hypothalamic and brain, pituitary, ovarian, and systemic based anovulation. Each system review includes diagnosis and treatment options.


The process of ovulation

To understand anovulation, one must first understand ovulation. Ovulation involves a progression of cellular changes in follicles that occur from fetal life until menopause.⁴ At any given time in the ovary follicles are at different stages of maturity. Primordial follicles progress to immature follicles and acquired hormone responsiveness by a process that remains unclear.^{5, 6} These small immature follicles, called resting follicles or antral follicles, are acted upon by several hormones to either progress to a growth phase or regress by atresia.⁴ Granulosa and theca cells of the follicle make up the two-cell system that is responsible for follicular growth.⁵ Gonadotropin hormones from the pituitary effect a structural change in these cells that causes the follicles to enlarge. The number of granulosa cells and theca cells within each follicle increases and a follicular fluid containing hormone products is accumulated in the follicle as it progresses through the growth phase.

Follicle stimulating hormone (FSH) is the primary gonadotropin responsible for this progression.⁴ As the follicles enlarge, FSH stimulates the production of more FSH receptors on the granulosa cells. This allows the follicle to become more sensitive to FSH and grow more rapidly. The larger follicles recruit more theca cells, which produce androstenedione. This androgen passes through the basement membrane and is converted to estradiol by FSH driven aromatization in the increasing number of granulosa cells.⁷ Once the follicle becomes large enough, cell growth slows and the cellular energy resources are used almost exclusively to produce these steroids. The increasing amount of estradiol produced in turn inhibits the release of FSH from the pituitary. Without FSH, the smaller follicles that contain fewer FSH receptors are no longer stimulated to grow and instead regress, leaving the dominant follicle for ovulation.

Follicular development is driven by FSH, but lutenizing hormone (LH) is responsible for ovulation. FSH acts on theca cells to induce LH receptor expression and render the cells sensitive to LH.⁴ LH also stimulates the theca cells to produce androstenedione, which is converted to estradiol by granulosa cells as described above. The estradiol produced further stimulates LH release from the pituitary. When a critical level of LH is reached, ovulation occurs and the follicle rapidly changes to a corpus luteum. Progesterone, produced by the corpus luteum, increases following ovulation and inhibits LH secretion by an effect on the hypothalamus.⁸ Without fertilization of the ova, the corpus luteum regresses, progesterone and estradiol levels drop, and FSH is again released to promote development of a new dominant follicle.⁴

The gonadotropins responsible for this series of events (FSH and LH) are released from the pituitary and are directly regulated by gonadotropin releasing hormone (GnRH).⁸ GnRH is secreted in a pulsatile pattern that becomes regular as women progress through puberty. This regular pattern is essential for proper production and release of LH and FSH. Several conditions of anovulation mimic the irregular GnRH pulse pattern seen in prepubescent girls further demonstrating the importance of the cyclic release of GnRH in normal ovulation. Estradiol and progesterone, which are produced as the dominant follicle develops, further regulate the release of GnRH. The hormone feedback and regulation of GnRH is mediated by catecholamines and endogenous opioids.^{9, 10}

In addition to the systemic gonadotropins, follicle development is also regulated by local hormones.⁷ Activin and inhibin are produced in the granulosa cells in response to FSH stimulation. Activin augments the FSH effects on granulosa cells and suppresses androgen synthesis, allowing for follicle growth. Inhibin is produced as the follicle develops and enhances androgen synthesis in theca cells.¹¹ The increased androstenedione is the substrate for estradiol production. Theca cells also respond to insulin-like growth factor II that further augments LH action.⁷

Anovulation can result from disruption of this series of events anywhere along the pathway.⁴ Several external factors such as stress and nutrition also cause anovulation by affecting the hypothalamus and the central nervous system. Disruption at the level of the pituitary causes reduced gonadotropin secretion. Polycystic ovary syndrome can be considered a physiologic state of anovulation that may be caused by disorder in one or more organ systems. Systemic disease has been shown to affect ovulation as well. This chapter reviews the causes of anovulation and how to treat this common problem.

Anovulation can result from disruption at any level in the hypothalamic–pituitary–ovarian (HPO) axis. Consequently, categorizing the different mechanisms of anovulation logically follows a systems approach. A systems approach breaks down the causes of anovulation into four categories:

• Hypothalamic and brain
• Pituitary
• Ovarian
• Systemic

It is important to remember that anovulation is affected by the health of the entire patient, therefore, some disorders can involve multiple levels of the HPO axis.


Anovulation due to disorder of the hypothalamus and brain     

The hypothalamic causes of anovulation result from decreased or dysfunctional production of GnRH. Pharmacological studies have shown GnRH release is regulated directly and indirectly by endogenous opioids, catecholamines, and dopamine.⁹ Dopamine stimulates the release of GnRH, whereas endogenous opioids block dopamine and consequently decrease GnRH. In patients with conditions of elevated endogenous opioids, treatment with naloxone blocks opioid receptors and results in a return of LH levels to normal.¹⁰

Corticotropin releasing hormone (CRH) is produced by the hypothalamus and blocks GnRH release. CRH is also produced in the amygdala.¹² The central nucleus of the amygdala mediates fear and anxiety by CRH producing neurons. These neurons project to several limbic structures and have been shown to decrease serotonin and increase beta-endorphin production thereby decreasing GnRH release. High levels of cortisol from the adrenal glands have also been associated with high levels of CRH implicating stress in anovulation.¹³

STRESS INDUCED ANOVULATION

Stress has been defined as a state of threatened homeostasis.¹⁴ The stress system is the mechanism by which the body tries to maintain homeostasis. Stress includes physical, emotional, and nutritional changes. Reproductive status mirrors the physiologic state and the external environment.¹⁵ When stress is significant reproductive function decreases in an effort to maintain homeostasis.¹⁶ Stress has also been shown to decrease pregnancy rates and increase miscarriage rates.¹⁷
      
The stress system is comprised of the hypothalamic–pituitary–adrenal (HPA) axis, arousal, and the autonomic system.¹⁸ The main chemical mediators of stress include CRH, glucocorticoids, and beta-endorphins. CRH has receptors in many different tissues including ovary, endothelium, hypothalamus, and inflammatory tissues. Produced in the hypothalamus, CRH and arginine vasopressin stimulate adrenocorticotropic hormone (ACTH) production in the pituitary. This increases cortisol production in the adrenal glands. Cortisol is a glucocorticoid that acts on multiple body systems and reduces LH, estradiol, and progesterone effects. Many of the effects of glucocorticoids and CRH in a stress response involve systematically inhibiting T helper (Th1) proinflammatory responses and induction of a Th2 shift.¹⁴

Beta-endorphins are secreted from nerve terminals in response to CRH and produce the initial euphoria of acute stress, necessary for survival.¹⁴ Dopamine has also been shown to increase during stress in a pattern correlating to cortisol levels.¹⁹ Estrogen has a direct effect on CRH release in stress and promotes CRH synthesis.²⁰ Elevated levels of CRH and cortisol suppress GnRH secretion and consequently decrease ovulation.¹⁵ Stress is a common problem in patients undergoing fertility workup and treatment. Techniques are currently being studied to reduce stress including acupuncture, yoga, and meditation.²¹        

FUNCTIONAL HYPOTHALAMIC AMENORRHEA

Functional hypothalamic amenorrhea (FHA) is defined as cessation of menses and ovulation without an identifiable organic cause.²² Examples of organic causes of anovulation include clinical eating disorders and significant weight.²³ FHA therefore is a diagnosis of exclusion with a reported incidence of 15–35%.²² As further understanding of anovulation develops, the number of patients diagnosed as FHA decreases.

Anovulation in FHA results from a decrease in GnRH release and consequently decreased gonadotropin release. Such patients also fail to menstruate after treatment with progesterone demonstrating low estrogen levels correlating to chronic lack of gonadotropin stimulation.²⁴ Slightly increased cortisol levels are typical with low to normal gonadotropins. Such patients do respond to pulsatile GnRH treatment further identifying the hypothalamus as the main cause for anovulation. LH pulse frequency is reduced and the interval between pulses is prolonged.²⁵
    
One hypothesis for FHA is a synergistic metabolic and psychosocial dysfunction similar to a state of chronic stress.²² FHA patients have been reported to have a higher likelihood of mood disorders, increased amount of exercise, mild weight loss, and diets with lower fat content, increased fiber, and increased carbohydrates.^{22, 23} Personality traits include perfectionism, low self esteem, and poor stress management ability.²³

Another evolving theory is that FHA is a spectrum of reduced gonadotropin secretion due to variable expression of a genetic form of anovulation.²⁶ This has been seen in males who show reversible hypothalamic hypogonadism and an identifiable genetic mutation (see below).²⁷ At the present time, similar genes have not been identified in women. This condition represents a state of GnRH resistance similar to insulin resistance. Due to the low estrogen and elevated cortisol levels, patients with FHA are at increased risk of bone loss and systemic disease.²² Treatment should involve nutritional and psychological counseling, however, this form of anovulation often resolves spontaneously.

PSYCHOGENIC TRAUMA AND STRESS

Studies have shown the impact of external factors in the environment on menstruation and consequently ovulation.^{13, 28, 29} Menstrual cycles in college women living together will begin to synchronize.²⁸These same women will have longer cycles when spending increasing time with male students. These changes are likely the result of pheromones influencing the hypothalamus. Further studies note the influence of psychological state on menstruation. In patients with clinical depression, cortisol levels were found to be significantly elevated.²⁹Other hormones including prolactin, gonadotropins, and estrogen are all normal in patients with psychological distress. When given exogenous GnRH, these patients have a normal release of LH and FSH suggesting a suppression of GnRH as the cause of anovulation associated with depression.

ANOREXIA NERVOSA

Anorexia nervosa is an eating disorder stemming from a disordered body image resulting in malnutrition and severe weight loss.³⁰ The diagnostic criteria includes amenorrhea implying a functional abnormality of the HPO axis.³¹ The prevalence is reported to be 0.5–1% in adolescents. Complications of anorexia nervosa include a mortality rate of 2–10% most often due to suicide and severe electrolyte disturbance. Bone density loss occurs as a result of low estrogen levels.^{31, 32} Anorexia differs from other forms of psychogenic anovulation. The ovulatory failure in anorexia is due to metabolic changes that occur with weight loss, while the underlying problem is psychological.
    
Gonadotropin levels are reduced in anorexia, as are leptin and estradiol.³² This hypoestrogenic state results in a thin endometrial lining that does not shed after progesterone treatment. Leptin levels, which correlate with body fat and nutrition status, have been found to play a role in ovulation and are discussed later in this chapter.³³ Triiodothyronine (T3) is decreased and reverse T3 is elevated, resulting in hypothyroid symptoms including dry skin and bradycardia.³² Growth hormone is also increased due to periods of starvation.
       
Several findings indicate that anovulation associated with anorexia arises at the level of the hypothalamus.^{30, 32, 34} The pulse frequency of gonadotropin release is similar to the pulse frequency seen in childhood.³⁰ Starvation has been shown to decrease GnRH release and subsequently decrease gonadotropins. When exogenous GnRH is administered in a physiologic pattern the gonadotropin pulse frequency normalizes and ovulation occurs.³⁴ Levels of CRH are also elevated, correlating with elevated cortisol and suppression of GnRH release.^{32, 35}

Anovulation with anorexia and hypothalamic suppression is not only due to low body fat. Nutritional status and physical activity play a key role in ovulation and treatment. Amenorrhea was noted to occur when weight dropped below 90% of ideal body weight, independent of body fat percentage.³⁶ In patients who gain appropriate amounts of weight, some remain anovulatory and show decreased gonadotropin levels. Anovulatory anorexics who weighed the same as ovulating anorexics were found to have higher levels of physical activity.³⁵ Low levels of leptin are also found in patients who have poor eating habits when controlling for weight.³³ As a result, treatment requires nutritional improvement, weight gain, and psychiatric care. This syndrome is serious and carries mortal consequences.

BULIMIA NERVOSA

Bulimia nervosa is another eating disorder associated with anovulation. Bulimia nervosa is defined as binge eating with subsequent compensatory behavior (purging) and a poor body image.³¹ Unlike anorexia, bulimics are not underweight. Fifty per cent of bulimics have amenorrhea.³⁷ Bulimics do have decreased levels of LH secretion much like patients with anorexia. Low LH in bulimia is found when body weight is less than 85% of previous highest weight independent of total body fat. Patients with bulimia are not hypoestrogenic and are at less risk for osteoporosis. However, persistently amenorrheic bulimics do have an elevated risk of endometrial cancer due to continuous estrogen stimulation of the uterus.³¹ Leptin levels in bulimic patients can be normal, but do decrease with poor nutrition.³³

PHARMACOLOGIC AGENTS

Estrogen and progesterone effect gonadotropin release indirectly using biogenic amines as intermediaries. Norepinephrine and epinephrine are responsible for signal transduction between the hypothalamus and the pituitary.³⁸ These amines increase 2 days prior to the LH surge.³⁹ Dopamine regulates prolactin and GnRH release and is blocked by endogenous opioids.^{11, 40} Drugs that affect metabolism and release of these amines will consequently effect changes in the HPO axis. Examples of these medications are given in Table 1. These drugs will often cause elevated LH and prolactin. FSH is generally not affected.

Table 1. Medications causing anovulation

One additional class of drugs that may affect ovulation is nonsteroidal antiinflammatory drugs (NSAIDs).⁴¹ Prostaglandins are important for ovulation and release of the ova from the ovary. Preovulatory follicles produce prostaglandins in response to the LH surge. NSAIDs block prostaglandin synthesis thereby preventing ovulation.⁴¹

POST-PILL ANOVULATION

Hormonal contraception has been associated with amenorrhea and a slow return to fertility after stopping therapy. The post-pill anovulation syndrome is historically defined as a failure to menstruate within 1 year of discontinuing hormonal contraception.⁴² Much of the data supporting a slow return to fertility was based on high dose hormone contraceptive pills.⁴³ Additionally, many patients taking hormone contraception may have underlying anovulation or subfertility. Currently there are several different vehicles for administering contraception. Current data support a similar return to fertility between most modalities.⁴² Patients with anovulation exceeding 3–6 months following discontinuation of oral contraceptive pills (OCPs) should have a workup for other causes of amenorrhea.
     
The pregnancy rate at 1 year after discontinuing combined oral contraceptive pills (COCPs) is the same as the pregnancy rate for people not previously taking birth control.⁴² Some data suggest women who had taken COCPs had more pregnancies than women who had not taken COCPs.⁴⁴ The hormone containing intrauterine device (IUD) and the nonhormone containing IUD do not significantly differ from COCPs in return to fertility rates.⁴² Fertility after discontinuing progesterone only contraceptive pills did not differ from nonhormone users. Data are not available for continuous use oral contraception, however, extrapolating from implantable and intrauterine device data there were no differences in pregnancy rates after discontinuation compared to noncontraception patients. The only modality that had a lower pregnancy rate at 1 year when compared to noncontraception users is subcutaneous depomedroxyprogesterone. In summary, pregnancy rates 1 year after stopping birth control are the same as pregnancy rates for women who do not use birth control. However, an evaluation workup should be performed in patients who have amenorrhea for more than 3–6 months after discontinuing OCPs.

HYPOTHALAMIC LESIONS

Tumors, inflammation, and degeneration of the hypothalamus can affect ovulatory function. Generally these events will lead to a reduction in gonadotropin release from the pituitary due to the tumor compressing the pituitary stalk.⁴⁵ Other hypothalamic tumors affect ovulation by secreting hormones.⁴⁶ Inflammatory lesions within the hypothalamus have been shown to decrease function by increasing levels of cortisol.⁴⁷

The most common hypothalamic tumor is the craniopharyngioma.⁴⁵ Other tumors include gliomas, dermoids, meningiomas, and germinomas.⁴⁸ In craniopharyngiomas, growth hormone, thyroxin, and gonadotropins are generally decreased.⁴⁵ Stimulation with GnRH does not produce an increase in gonadotropins suggesting a dysfunction in the blood supply to the pituitary due to the tumor. When hormonally active tumors are removed, the symptoms of hormone excess rapidly improve.⁴⁸ Inflammatory lesions have been seen in tuberculosis and sarcoidosis causing low gonadotropins.^{47, 49} Treatment for anatomic defects involves treatment of the underlying cause.

CONGENITAL DEFECTS

Hypothalamic hypogonadism can be associated with a genetic syndrome or several single gene mutations. Kallmann’s syndrome is a deficiency of GnRH and concurrent anosmia.⁵⁰ This rare disorder has an incidence of 1:50,000.⁵¹ These patients have a migration defect of GnRH secreting neurons from the thalamus and agenesis of olfactory neurons.⁵⁰ Several mutations of the KAL-1 gene have been associated with the X-linked form of this syndrome, however, most cases are sporadic mutations.^{50, 52} Both LH and FSH are decreased as expected due to the GnRH deficiency. Follicles are seen in early stages of maturation and successful pregnancy has occurred using gonadotropin therapy.⁵¹

Idiopathic hypogonadotropic hypogonadism (IHH) is a collection of genetic mutations that result in delay of puberty, infertility, and low gonadotropins.⁵³ One X-linked recessive mutation is adrenal hypoplasia congenita (AHC), which is similar to congenital adrenal hyperplasia (CAH) but does not have hyperandrogenism. AHC gene mutation results in production of an abnormal DAX1 protein that regulates gonadotropin secretion in the hypothalamus and pituitary. Several other genes associated with IHH include KAL1, FGFR1, GNRHR, and NELF.²⁶ Mutations in these genes show incomplete penetrance and variable phenotype in men and resolution has been reorted.²⁷ It remains to be shown if women also have a reversible subtype of IHH. Women with IHH have hypoestrogenism, amenorrhea, and low gonadotropin levels. Leptin mutations and leptin receptor mutations are another cause of IHH.⁵³ Mutations have also been found in the beta subunits of several pituitary hormones including LH, FSH, and thyrotropin and are discussed later in this chapter.

Another congenital cause for hypothalamic hypogonadism is Bardet-Biedl or Laurence-Moon syndrome. Recent literature supports that these two syndromes are variants of the same genetic abnormalities.⁵⁴ These patients present with a variable phenotype including obesity, polydactyly, retinal and renal abnormalities, and hypogonadism. This is a rare autosomal recessive syndrome with an incidence of 1:125,000 to 1:160,000. Several gene mutations have been isolated in these patients that encode for ciliary movement which is essential for normal organ development.⁵⁵ LH and FSH levels can be variable.⁵⁶ When given GnRH stimulation, these patients have a LH response similar to pubertal girls.⁵⁷ When given thyrotropin releasing hormone, the TSH secretion of these patients is normal, suggesting anovulation is due to hypothalamic dysfunction.

Pituitary anovulation

Normal ovulation requires communication between the hypothalamus, pituitary, and ovary. The HPO axis is complex and is influenced by several other processes in the body. The pituitary gland acts to enable communication between the hypothalamus and the ovary. The gland is composed of an anterior and a posterior lobe. The anterior lobe secretes gonadotropins in response to GnRH from the hypothalamus to produce an effect on the ovary. By this means, the pituitary acts as an endocrine intermediary between the brain and the gonads. Hormone feedback regulates the rate of secretion to maintain regular ovulation and coordinate sexual function. Overgrowth of pituitary cells or vascular injury can occur and disrupt or alter production of hormones. Additionally, abnormal hormones can be produced by the pituitary resulting in ineffective pituitary function.

PITUITARY TUMORS

Pituitary tumors comprise 10–20% of all brain tumors.⁵⁸ They are classified as macroadenomas if the size is greater than 10 mm or microadenomas if less than 10 mm. Clinically, pituitary tumors can be either functional or nonfunctional depending on whether or not the tumor produces hormones. Seventy per cent of pituitary tumors are functional. Forty-five per cent of adenomas secrete prolactin.⁵⁹ Most functional pituitary tumors are microadenomas, however, many patients with macroadenomas have menstrual abnormalities.⁵⁸ Due to the lack of hormone production, macroadenomas may be diagnosed only when they cause visual problems from compression of optic nerves. Microadenomas most commonly present with hormone abnormalities.
        
Macroadenomas cause anovulation due to compression of the pituitary as the mass enlarges.⁵⁸ The blood supply to the pituitary from the hypothalamus is the means for hormone control of gonadotropin release.⁶⁰ Compression of the vessels, the gland, or both results in decreased production of pituitary hormones and subsequent anovulation. As the mass grows and compresses the pituitary, endocrinologists have often observed that the first hormone to be lost is growth hormone, followed by gonadotropins.⁵⁸ Some patients with macroadenomas ignore menstrual irregularities for years before seeking care. In patients seeking fertility treatment, pituitary tumors are often detected earlier on magnetic resonance imaging (MRI).
        
Microadenomas often produce elevated levels of prolactin, which causes anovulation.⁶¹ Of patients with hyperprolactinemia, 20–25% will have galactorrhea. Elevated levels of prolactin cause a positive feedback to dopamine release. Dopamine increases cause a decreased release of GnRH. There are also direct effects of prolactin on the ovary and pituitary decreasing ovulation.^{62, 63} Gonadotropin secreting tumors have been reported as well.⁶⁰ Serum LH and FSH levels are abnormal in such patients, indicating gonadotropin release is not under the control of GnRH.
        
Sarcoidosis is a chronic inflammatory disease, which results in the formation of granulomas in multiple organ systems.⁶⁴ Sarcoidosis has been found in the pituitary and can cause anovulation.⁶⁵ The mechanism of anovulation from sarcoidosis is believed to be a compression of the gland by the granulomas, much like macroadenomas. Treatment involves steroid replacement and radiation therapy, but due to the progressive nature of the disease these therapies have not been very successful.

ISCHEMIA

Vascular compromise to the pituitary blood supply can result in anovulation. This is known as pituitary apoplexy.⁶⁶ Several situations can lead to vascular injury including tumor compression of blood supply, cerebral vascular accident, hemorrhage causing shunting of blood from the pituitary, and diabetes. Sheehan’s syndrome is ischemic damage to the pituitary resulting from vascular changes at the time of parturition.⁶⁷ Sickle cell disease has also been seen with hypopituitarism.⁶⁸ Infections can also lead to damage to the pituitary gland.⁶⁹ Ischemia of the pituitary gland most often results in loss of all hormones, unlike the sequential loss seen with tumor expansion. Empty sella syndrome is another condition in which the pituitary is not visualized within the sella turcica and results in partial loss of pituitary function.

PITUITARY HORMONE DEFECTS

Another pituitary cause of anovulation is abnormalities in the pituitary hormone structure. LH and FSH have two subunits, alpha and beta. The alpha subunit structure is very consistent, while the beta subunit can vary.⁷⁰ Mutations in the structure of the beta subunit can interfere with binding to the alpha subunit and consequently cause an inability to function.⁷¹ Patients with FSH abnormalities have delayed puberty and decreased sex hormones along with anovulation. Because the beta subunit differs for each hormone these abnormalities only affect one gonadotropin.⁷² The diagnosis can be determined by administering GnRH, which results in normal elevation of only one hormone, generally LH.⁷³

One characteristic of gonadotropins that may contribute to abnormal hormone structure is variable bioactivity.⁷⁴ LH has a bioactive type and an immunologic or inactive type. In patients with anovulation there appears to be a higher concentration of bioactive LH when stimulated with GnRH. The types of FSH are more variable and consequently may be more prone to abnormal production.⁷⁰


Ovarian causes of anovulation

The ovarian follicle requires hormone stimulation to develop.⁴ Gonadotropins act on the ovary to promote growth and maturation of primordial follicles into a dominant follicle. In return, steroid hormones are produced by the ovary and act as feedback to regulate the ovulation system. Defects in ovarian function affecting ovulation include a lack of follicles to develop, an abnormality in steroid secretion, or lack of communication between the gonadotropins and the ovarian receptors. Gonadotropins are elevated in ovarian dysfunction because estrogen levels are low.⁷⁵ The normal feedback signal to the hypothalamus is absent. Inhibin is another substance produced by the follicle that inhibits FSH release.⁷⁶ Although estrogen replacement is important to reduce health risks associated with hypoestrogenemia, estrogen alone does not correct the gonadotropin elevation when inhibin is deficient.

POLYCYSTIC OVARY SYNDROME

One of the more complex conditions associated with anovulation is polycystic ovary syndrome (PCOS). The criteria defined by the PCOS Consensus Workshop Group (Rotterdam) require two of three features for the diagnosis of PCOS.⁷⁷ These features include clinical or biochemical evidence of hyperandrogenemia, oligoovulation or anovulation, and polycystic appearing ovaries.⁷⁷ Using these criteria, the incidence of PCOS is greater than 5% in women of reproductive age.⁷⁸ Common laboratory findings with PCOS include elevated LH, androgens, and estrogen, with normal or low FSH.⁷⁹ In many but not all patients with PCOS, insulin insensitivity and obesity are seen.

The occurrence of polycystic ovaries in the general population is common.⁷⁹ Twenty-two per cent of ovulating women will have polycystic appearing ovaries on ultrasound. However, 73% of anovulatory women will have polycystic ovaries. The presence of polycystic ovaries does not increase the risk of developing PCOS in the future.⁸⁰ However, if present with oligomenorrhea there is an increased risk of developing PCOS.⁷⁹

The cause of anovulation in PCOS involves dysfunction of the normal cyclic nature of the menstrual cycle and can arise by several different mechanisms. Abnormal antral follicle development and function is a fundamental feature.⁷⁸ The cystic appearance of the ovaries results from several follicles failing to mature properly without development of a dominant follicle. The multiple follicles produce large amounts of estradiol, which inhibits FSH release thereby preventing further follicular development. Anti-mullerian hormone (AMH) may be involved in regulating the progression of follicles into growth phase, and abnormalities in AMH have also been proposed as contributors to the etiology of PCOS.

Half of PCOS patients are obese.⁷⁷ Obese patients with PCOS are more likely to be anovulatory and have symptoms of excess androgens.⁷⁸ Excess adipose tissue increases peripheral conversion of androgens to estrone, which inhibits ovulation at the hypothalamus. Obese patients with PCOS have a higher incidence of insulin resistance than obese patients without PCOS. Elevated insulin and insulin insensitivity play a role in anovulation and hyperandrogenemia. High levels of insulin stimulate the theca cells to increase androgen production via insulin-like growth factors.⁷⁷ Elevated androgens further arrest follicular development and result in anovulation. Weight loss of 5–10% of body weight in obese patients will increase ovulation. Obesity and hyperinsulinemia increase the risk of developing metabolic syndrome and subsequently significantly increase mortality from cardiovascular events.⁸¹ Hyperestrogenemia from chronic anovulation increases the risk of developing uterine and breast cancer as well.⁸²

Treatment of PCOS requires understanding of the goals of the patient. Chronic anovulation with unopposed estrogen should be treated with cyclic progesterone withdrawal.⁸² Symptoms of hirsutism can be managed with anti-androgens and oral contraceptives with anti-androgen attributes. For patients desiring pregnancy, the first line of treatment should be weight loss.⁸³ Weight loss of 5–10% of body weight has a 50% return to ovulation and a 33% pregnancy rate within 6 months. If weight loss alone is not successful, clomiphene citrate can be used.⁸⁴ The ASRM 2008 guidelines state glucophage can be added to clomiphene citrate if not successful, but there is no benefit to glucophage alone for ovulation induction. All PCOS patients should be screened for diabetes mellitus with a 2-hour glucose tolerance test (GTT) and hyperinsulinemia should be treated.⁸⁵ Laparoscopic ovarian drilling (LOD)⁸⁴ has been used; however, the procedure causes destruction of primordial follicles and most specialists eschew this treatment in women interested in future fertility. Finally, gonadotropin therapy or IVF are options if other strategies for ovulation induction are not successful.

NONPSYCHOGENIC WEIGHT DISTURBANCES

In 1–5% of women, amenorrhea is related to their body weight.⁸⁶ Amenorrhea occurs when women lose 10–15% of their normal body weight.⁸⁷ However, absolute body mass or fat content is not as important in ovulation as energy balance. Energy balance involves the amount of energy supply and the amount of usage. In a study of nonathletes, 43% became anovulatory when they started aggressively exercising.⁸⁸ These patients had a rapid increase in energy expenditure accompanied by weight loss. In trained athletes, cortisol and CRH levels are elevated implying a suppression of GnRH and subsequent decrease in LH causing anovulation.⁸⁹ Similar decreases in LH are seen in weight loss alone which resolve with weight gain.^{88, 90} The state of gonadotropin suppression seen in women with a negative energy balance results in hypoestrogenemia and increases the risk of decreased bone density.⁹¹ This low estrogen state is further seen by the presence of vaginal atrophy in nonanorexic malnourished women.⁹²
   
The other weight related anovulatory condition is obesity. Obesity is currently of epidemic proportions in the US with a prevalence of 21% of the population increasing by 1–6% annually.⁸⁷ Unlike undernourished patients, obese patients have a state of energy surplus. Most commonly obesity is a result of a sedentary lifestyle, but genetics may play a role. Anovulation in obesity results from excess androgens and estrogen causing decreased progesterone.⁹³ The LH pulse amplitude is also diminished.⁹⁴ Adipose tissue is highly metabolically active and produces 50% of premenopausal testosterone.⁸⁷ Further metabolic changes seen in obesity include decreased sex-hormone binding globulin, FSH, prolactin, and cortisol.⁹³ Estrone is significantly increased by peripheral conversion in adipocytes. In addition to anovulation, obese patients have increased risks of spontaneous abortion, IVF failure, and require higher doses of clomiphene citrate and gonadotropins.⁸⁷ Modest weight loss of 10% of body weight does increase ovulation rates. Bariatric surgery has also been successful in improving ovulation.⁹⁵ The improved ovulation following gastric bypass is directly proportional to the amount of postoperative weight loss.

ROLE OF LEPTIN IN ANOVULATION

Leptin is a protein produced by adipose cells that acts as a hormone on the reproductive axis.⁹⁶ Serum levels of leptin fluctuate with eating and are indicators of energy stores. Reproduction requires energy and leptin acts as a signal to the HPO axis when adequate energy is present for ovulation.⁹⁷ Leptin receptors have been found in several endocrine tissues including hypothalamus, anterior pituitary, granulosa and theca cells, and interstitial cells of the ovary. Insulin and estrogen stimulate leptin production while androgens decrease production.

The effects of leptin on hormones of the HPO axis vary with different physiologic states. GnRH pulsatility is increased indirectly via afferent interneurons of the hypothalamus in response to leptin.⁹⁸ LH release is directly stimulated as is FSH to a lesser amount.⁹⁷ Since leptin is an indicator of energy availability, it is understandable that leptin levels will be low in starvation such as anorexia and underweight women. This is also present in hypothalamic amenorrhea. Consequently, ovulation is inhibited by the absence of leptin stimulation of GnRH release. Exogenous administration of leptin increases LH pulse frequency in these patients independent of body mass.⁹⁹ Conversely, in obesity and PCOS leptin levels are significantly increased.^{97, 100} Very high levels of leptin antagonize factors involved in LH and FSH release and suppress estradiol production thereby preventing ovulation.⁹⁷ Leptin acts as a regulatory hormone and decreases ovulation in conditions of extreme energy imbalance. The role of leptin in the diagnosis and treatment of anovulation is still being studied.

PSEUDO-OVULATION/LUTEINIZED UNRUPTURED FOLLICLE

Luteinized unruptured follicle syndrome (LUF) may be a rare cause for transient anovulation and has been linked to NSAID use.¹⁰¹ Prostaglandins are important for follicle rupture and ovulation. Indomethacin, an NSAID, induced a 50–100% occurrence of LUF. Fertility returns after cessation of NSAIDs. Due to low recurrence rates, fertility rates were similar between patients with LUF and controls.  Because of the high prevalence and transient nature, current thinking is that LUF is not a true cause of infertility.

OVARIAN TUMORS

Neoplasms of the ovary can cause anovulation by several mechanisms. Tumors in the ovary can disrupt the stroma and decrease normal oocyte release.¹⁰² Some nonhormone secreting tumors release additional substances that increase androgen production. This excess androgen is converted by aromatase in the peripheral tissues to estrogen, which prohibits ovulation. Ovarian tumors can also produce hormones.¹⁰³ Abnormal levels of gonadotropins disrupt the normal ovulatory cycle and prevent ovulation.

PRIMARY OVARIAN INSUFFICIENCY     

Menopause is the cessation of menses for more than 1 year signifying a completion of ovarian function. The average age of menopause is 50 years old.¹⁰⁴ Loss of ovarian function results from the depletion of follicles and therefore may be mistaken for anovulation. Primary ovarian insufficiency (POI) is the depletion of follicle reserve prior to age 40.¹⁰⁵ This can be due to either absence of follicles or abnormal ovarian function.¹⁰⁶ POI occurs in approximately 1% of all women.¹⁰⁷ Most often POI is spontaneous and the cause is unknown. POI is reviewed here because in some cases the syndrome is transient, with resulting ovarian function and because POI must be distinguished from other causes of anovulation.

The most accepted definition of POI is disorganized menses or anovulation for more than 4 months prior to age 40.¹⁰⁵ Included are serum FSH measurements in the menopausal range on two occasions more than 1 month apart. Patients with POI have low estrogen levels often at an early age and hormone replacement is important for bone and cardiovascular health.¹⁰⁸ The term POI has replaced the more finite term “premature ovarian failure” because this syndrome occurs as a continuum and a small number of patients may conceive after the diagnosis of POI.¹⁰⁵

Several abnormalities in ovarian function can cause POI. Mutations in the gene coding for the FSH receptor prevent FSH from binding to the signaling receptor.⁷⁵ FSH is required for follicle maturation and estrogen production, consequently, these patients have anovulation and hypoestrogenemia. These receptor gene mutations are called inactivating mutations due to the effective block of FSH activity.¹⁰⁹ Activating gene mutations also occur. These mutations present with increased function of the FSH receptor often binding other ligands.¹¹⁰ FSH receptor function can also be affected by autoantibodies binding receptor sites.⁷⁶

A condition previously called Savage syndrome, or ovarian resistance, is marked by anovulation with elevated FSH and a normal karyotype. The ovaries will show multiple primordial follicles from the lack of FSH stimulation. Unlike FSH receptor mutations, successful pregnancies have been achieved with hormone replacement in patients with Savage syndrome.¹¹¹ Current studies have examined ovarian resistance at a molecular level, thereby drawing doubt onto the existence of Savage syndrome as an independent disorder.

Autoantibodies have been associated with POI and 33–61% of unexplained infertility cases.^{111, 112} Autoimmune polyglandular syndrome (APS) is a condition with autoantibodies affecting multiple systems.¹¹¹ Three types have been identified with APS type 1 having the highest correlation to POI. Autoantibodies have been found to bind gonadotropin receptors leading to anovulation. Addison’s disease has the best known association with autoimmune ovarian insufficiency.¹¹³ POI occurs in 10–20% of patients with autoimmune adrenal insufficiency.¹¹⁴ Autoantibodies targeting adrenal cells also target theca cells and steroid producing cells leading to anovulation. Viral infections such as mumps cause oophoritis and POI.¹¹⁵ The amount of ovarian function depends on the age at which the patient was exposed to the myxovirus.

Absence of follicle development also leads to POI and is mostly due to genetic abnormalities. These patients have “streak ovaries” due to the early loss of follicles in utero or before the onset of puberty. Pure gonadal dysgenesis, also called XXGD, is a poorly understood condition.¹¹⁶ The etiology of this genetic abnormality is not known, but occurrence has been associated with consanguinity. This autosomal recessive disorder is rare with an estimated incidence of 1:8300. Other gene mutations include FOXL2 and NR5A1.^{117, 118} FOXL2 mutation is associated with blepharophimosis/ptosis/epicanthus inversus (BPE) syndrome type 1.¹¹⁷ Mutations in FOXL2 gene produce abnormal proteins on the forkhead domain resulting in abnormal signal transduction.  NR5A1 inactivation causes ovarian hypoplasia.¹¹⁸ DIA, ZFT, and XIST gene mutations are also linked to POI.^{119, 120}

Rapid follicle atresia results in variable onset POI. The most common genetic defect is Turner syndrome. These patients have rapid follicle atresia before the onset of puberty resulting in “streak ovaries”.¹⁰⁶ Because the rate of atresia is rapid and follicles are initially present in the ovaries, 20–30% of these patients will reach spontaneous puberty. Of this group, 5–10% will be fertile prior to complete loss of follicles. There have been reports of successful pregnancies using donor eggs in patients with Turner syndrome. Patients with earlier ovarian failure should be given hormone replacement to prevent bone density loss.

FMR1 gene mutation is associated with accelerated follicle atresia and fragile X syndrome.¹²¹ The mutation occurs in 2% of spontaneous 46,XX POI and 14% of spontaneous 46,XX POI with a family history.¹⁰⁵ Additionally, 13–25% of fragile X syndrome carriers have POI.¹¹⁹ Because FMR1 mutation occurs frequently with POI, and because the X-linked condition carries a risk of mental retardation in males, this gene mutation should be screened for in the workup of a nonsyndromic patient with POI. Galactocemia is another genetic disorder with a high risk of POI.¹²² POI has also resulted from exposure to chemical solvents containing 2-bromopropane.¹²³ This exposure resulted in arrest of follicular development with recovery of ovarian function and pregnancy in two patients.

Systemic anovulation

ACUTE AND CHRONIC DISEASE

Chronic anovulation is seen in illness and stress caused by chronic illness.¹²⁴ This results from either the diseased organ system altering reproductive hormone levels or elevated stress hormones affecting the HPO axis as noted above. Cytokines are elevated in systemic disease, which can directly inhibit reproductive hormone producing organs.¹²⁵ As health status improves, reproductive function often resumes. With many chronic diseases, however, as fertility returns, pregnancy may negatively impact a patient’s health.

RENAL DISEASE

Early renal insufficiency results in decreased fertility and low libido. In children, onset of puberty is delayed.¹²⁶ With development of chronic renal failure, anovulation occurs. LH pulse frequency decreases resulting in loss of the LH surge and subsequent anovulation. The LH to FSH ratio is slightly increased but the LH response to GnRH stimulation is delayed. Hyperprolactinemia is often seen due to increased prolactin secretion and decreased renal clearance. Menstruation resumes with dialysis or renal transplant.¹²⁴ Ovulation is seen in 82.1% of patients following renal transplant.¹²⁶

LIVER DISEASE

The effect of liver disease on fertility depends on the age of onset and etiology. Children with liver disease will have delayed puberty by 1.1 years on average.¹²⁶ Full sexual development returns within 3 years of transplant. Gonadotropin measurements are normal in viral hepatitis, however, anovulation is seen. Hyperestrogenemia occurs due to aromatization of weak androgens from the portal circulation and consequently ovulation is prevented. Women with alcoholic hepatitis have early menopause. In alcoholics 20–40 years old, decreased numbers of follicles are seen and no corpora lutea are seen. Cirrhosis is associated with obesity and consequently estrogen levels may be elevated from peripheral conversion.¹²⁴

Secondary amenorrhea occurs in 50% of women with end stage liver disease (ESLD).¹²⁶ Menstrual irregularity is often the presenting complaint leading to the diagnosis of liver disease. In premenopausal patients with ESLD, gonadotropin levels are decreased as are estrogen and testosterone. These patients do not respond well to GnRH stimulation or clomiphene citrate. Following liver transplant 95% of patients under 45 years old will resume menses. Infertility in this population is 25–50% following transplant.

THYROID DISEASE

Thyroid disease is a common cause of menstrual cycle irregularity. Oligomenorrhea and amenorrhea occur in 58% of patients with hyperthyroidism.¹²⁷ Anovulation occurs in severe untreated disease. Gonadotropins are elevated in hyperthyroidism, as is sex hormone binding globulin (SHBG). The elevation in SHBG leads to an increase in total testosterone. Hypothyroidism presents with menorrhagia. Anovulation results from elevated thyroid stimulating hormone, which acts as a releasing factor for prolactin, and elevated levels of prolactin in turn contribute to anovulation as described previously.

ADRENAL DISEASE

Adrenal hormones are involved in the regulation of ovulation. In acquired adrenal insufficiency autoantibodies also may block FSH receptors.¹¹³ Congenital adrenal hyperplasia is associated with delayed puberty and amenorrhea.¹²⁸ Glucocorticoids are decreased and androgenic precursors are increased. Follicles are present in the ovaries but ovulation does not occur because of the excessive levels of androgens.

HIV    

Ovulation studies in HIV are conflicting. Patients with HIV are exposed to several medications and often have concomitant infections. Some studies show anovulation in HIV positive women correlates to the normal population. Other studies report worsening ovarian function with decreased CD4 cell counts.² Consensus maintains that there is currently no difference in ovulation rates in HIV positive women compared to noninfected women.

The most important consideration in the workup of anovulation is to determine the patient’s goals. Treatment of the patient who wants to get pregnant differs from that of the patient who is concerned about the risks of early menopause. In patients who desire pregnancy, the clinician needs to determine if they are actively trying for pregnancy, or are planning for pregnancy several years in the future. The approach outlined below begins with the patient who is actively trying for pregnancy.

History

Many patients with anovulation will present with amenorrhea. Primary amenorrhea is failure to menstruate and no secondary sexual characteristics by age 14 or no menstruation by age 16 with normal sexual development.¹²⁹ Secondary amenorrhea is the cessation of menstruation for more than 3 months.¹³⁰ The etiologies of primary and secondary amenorrhea differ. Primary amenorrhea is often seen in congenital disorders.¹³¹ The most common cause of secondary amenorrhea in women of childbearing age is pregnancy, consequently the workup for anovulation should begin with a pregnancy test.          

Details of a patient’s previous medical history can direct the evaluation of anovulation. Chronic disease can affect ovulation and may increase risks during pregnancy.¹³² Psychiatric problems are also often associated with ovulation dysfunction. The use of any antipsychotic medications should be noted.⁴⁰ Details of previous pregnancies are likewise important in the evaluation of ovulation and can help distinguish genetic disorders from later onset anovulation.

Physical

The physical exam should include an evaluation of vital signs, height, weight, BMI, and appearance. Obesity is commonly associated with anovulation and PCOS.⁷⁷ Very thin patients may have anorexia or nutritional deficits. Hirsutism may suggest PCOS, CAH or an androgen secreting tumor. Visual field testing is useful in patients who report visual changes suggesting a pituitary tumor. Palpation of the thyroid and abdomen should also be performed to evaluate for masses. Evaluation of the patient with primary amenorrhea should include a bimanual exam to determine the presence of a patent outflow tract and uterus.

Laboratory tests

In patients with amenorrhea, pregnancy should be considered and a pregnancy test performed early in the workup. Evaluation of the HPO axis should be performed in a stepwise fashion. Serum estradiol and gonadotropins determine ovarian function. FSH measurements have been standardized for day 3 of the menstrual cycle. However, in patients with amenorrhea a random FSH is appropriate. Measurement of LH has limited clinical use. The ratio of LH to FSH has been studied for PCOS but is not included in the definition of the syndrome and is therefore not necessary.⁷⁷

Elevated FSH indicates an ovarian problem. In patients under 30 years old with an elevated FSH, a karyotype should be performed. An increased risk of ovarian cancer is seen in XY females with gonadal dysgenesis.¹³³ Turner syndrome (45,XO) is associated with increased risk for cardiovascular, thyroid, and renal disease.¹³⁴ For these patients, a karyotype is very useful in the workup particularly relating to future pregnancy and health. In patients with elevated FSH and a normal karyotype, ovarian resistance and POI are considered. A trial of ovulation induction may be performed using clomiphene citrate as described later. If there is no benefit of clomiphene, exogenous gonadotropins may be effective.

Normal or decreased FSH values suggest dysfunction of the HPO axis. Subsequent testing includes prolactin, TSH, and T4. Thyroid abnormalities are very common and may be seen in up to 4% of patients with infertility.¹³⁵ Treatment for thyroid disease often restores HPO axis function. Hyperprolactinemia should direct the clinician to obtain an MRI of the pituitary. Serum prolactin levels greater than 250 μg/L are seen in prolactin secreting macroadenomas.¹³⁶ Macroadenomas may require surgery, while many microadenomas can be successfully treated with medical therapy.¹³⁷

In patients with signs of hirsutism, serum androgens including testosterone and dehydroepiandrosterone (DHEAS) can be evaluated. A testosterone level is a useful androgen test in determining the cause of hirsutism in women.¹³⁸ Elevated free testosterone is seen in 70% of women with PCOS. Due to technical limitations in testing for free testosterone, measurement of total testosterone can be used. DHEAS is produced primarily from the adrenal gland and elevated levels suggest an adrenal tumor. Many androgen-secreting tumors, however, cause severe signs of hyperandrogenism including virilization and clitoromegally.¹³⁹ A normal DHEAS level should direct attention to the ovary as the origin of excess androgens. Another useful hormone test in hirsutism is 17-hydroxyprogesterone. This is produced in the adrenal gland and the ovary, and is elevated in CAH. Most patients with hirsutism and PCOS will have elevated testosterone levels, while only 25–35% will have elevated DHEAS.¹³⁸

An additional laboratory test for patients with PCOS is a 2-hour GTT.⁸⁵ This test involves examining insulin and glucose levels following administration of a 75 g glucose bolus.¹⁴⁰ The glucose tolerance test is useful for determining insulin resistance. Additionally, obese PCOS patients are at increased risk for dyslipidemia and metabolic syndrome and a serum lipid profile is appropriate.¹⁴¹ Elevated lipid levels, particularly in young patients, may increase the risk of cardiovascular disease later in life. Diet, weight loss, and lifestyle modifications should be recommended to patients with metabolic syndrome risks.

Imaging tests

Ultrasound is an invaluable tool for the evaluation of gynecologic problems including the assessment of ovarian architecture, which is a criterion for the diagnosis of PCOS. Transvaginal ultrasound provides a reliable measurement of the thickness of the endometrial lining.¹⁴² A thickened endometrial lining suggesys the presence and effect of estrogen. Long term anovulation leads to chronic estrogen stimulation of the uterus and increases the risk of uterine cancer.¹⁴³ Since there is not good correlation between thickness and absence of endometrial hyperlasia or cancer,¹⁴⁴ it is justified to sample the endometrial lining in chronic anovulatory patients independent of the endometrial thickness. Ultrasound can also be used to evaluate the ovaries and measure the number antral follicles. Antral follicle count is a sensitive test for determining ovarian reserve and response to ovarian stimulation.¹⁴⁵ A low number of antral follicles during the follicular phase of the menstrual cycle is an indication of poor ovarian reserve. Ultrasound evaluation of the ovary is useful in the diagnosis of PCOS. To satisfy the definition of polycystic ovaries, each ovary must contain more than 12 follicles 2–9 mm in size or a calculated ovarian volume more than 10 mL.¹⁴⁶

Combined approach

With anovulation it is important to combine several tests in order to completely evaluate the patient. An example of this is the evaluation of diminished ovarian reserve. Combining patient demographics such as age with serum FSH, anti-mullerian hormone and antral follicle count gives a more accurate assessment of a patient’s chances of successful pregnancy.¹⁴⁷ Counseling patients about proper nutrition, weight management, and stress reduction can enhance fertility even when other causes of anovulation are determined.
         
Some patients plan to delay pregnancy either for weight management or because they are undergoing therapy for other medical conditions.  For women who are chronically anovulatory and have unopposed estrogen stimulation of the uterus, it is important to treat with progesterone on a regular basis to reduce the risk of endometrial cancer.¹⁴² For anovulatory women without estrogen, hormone replacement should be considered for bone health.¹⁴⁸


Ovulation induction

The treatment for anovulatory women who desire pregnancy varies based on the cause of their anovulation. If anovulation is due to a tumor or medical condition, treatment of the underlying cause may improve ovulation. For example, patients with hyperprolactinemia often resume ovulation after treatment with a dopamine agonist, and this should be evaluated before treating with ovulation inducing agents.¹⁴⁹

Clomiphene citrate is the first-line medical treatment for ovulation induction.¹⁵⁰ It is a selective estrogen receptor modulator that increases ovulation by binding estrogen receptors in the hypothalamus.¹⁵¹ This blockade causes increased GnRH release and increases ovulation. The starting dose of clomiphene is 50 mg daily for 5 days beginning on day 2 of the menstrual cycle.¹⁵² This can be increased by 50 mg per day for each subsequent cycle if pregnancy does not occur. The maximum dosage of clomiphene is 200 mg per day. Clomiphene citrate is useful for increasing GnRH release, however, it requires endogenous hormone production.

In cases of clomiphene failure gonadotropin therapy is often used to induce ovulation. Gonadotropins include human menopausal gonadotropins (hMG) or recombinant synthetic FSH and LH.¹⁵³ For PCOS patients who fail clomiphene, FSH treatment is often effective due to the endogenously high levels of LH present in PCOS.⁸⁴ In hypothalamic hypogonadotropic anovulation both FSH and LH replacement are required and it is advisable to begin with very low doses of LH for several weeks before FSH is added. Dosing regimens vary, but many centers start with a low dose such as 37.5–75 IU per day for 7–12 days until a dominant follicle 16–18 mm is present.¹⁵⁰ After development of a dominant follicle, human chorionic gonadotropin (hCG) or a GnRH agonist is administered to induce oocyte release. Progesterone support during the induced luteal phase should be considered because endogenous hormone production may be insufficient.           
Several considerations apply with ovulation induction for certain anovulatory etiologies. Many studies have evaluated the use of metformin for ovulation induction in PCOS.^{152, 154} There does not appear to be a benefit to using metformin alone for ovulation induction in PCOS patients, however, it is beneficial in managing insulin insensitivity in these patients.¹⁵² In addition, many patients with hypothalamic anovulation do not ovulate with clomiphene citrate. It is reasonable to begin using gonadotropins to treat such patients without a trial of clomiphene. In conclusion, there are many causes of anovulation. Proper treatment must include correct assessment of the underlying cause of anovulation, treatment of any identifiable conditions, and if appropriate ovulation induction using clomiphene citrate or gonadotropins.