Menstrual Irregularity: Hypothalamic, Pituitary & Ovarian Etiologies

Learning Objectives and Clinical Overview

• Goal of Study: Understand Abnormal Uterine Bleeding (AUB) including etiologies, clinical presentation, diagnosis, and treatment for conditions affecting the hypothalamus, pituitary, and ovaries.

• Major Disorders of Focus:

  • Hypothalamus: Functional Hypothalamic Amenorrhea (FHA), hyper- and hypothyroidism, medication-induced hyperprolactinemia, and congenital GnRH deficiency (Kallman Syndrome).

  • Pituitary: Benign functioning and non-functioning tumors (prolactinomas), cancers, infiltrative diseases, and Sheehan’s syndrome.

  • Ovaries: Polycystic Ovary Syndrome (PCOS), also known as Polyendocrine Metabolic Ovarian Syndrome (PMOS), and Primary Ovarian Insufficiency (POI).

• Key Emphasis: Detailed pathophysiology, long-term health risks, and management strategies for the two most common causes of anovulatory uterine bleeding: FHA and PCOS.

• Terminology Note: While terms like "females," "women," or "patient" are used to describe those with female pelvic anatomy, it is recognized that not all individuals who identify as women have female pelvic anatomy, and not all people with female pelvic anatomy identify as women. Healthcare providers are encouraged to provide affirming care to transgender men and gender-nonbinary individuals.

The Hypothalamic-Pituitary-Ovarian (H-P-O) Axis

• Hypothalamic Function: The hypothalamus integrates complex inputs including temperature, water balance, autonomic inputs, sensory/emotional/physical stress, energy stores, time/circadian rhythms, and sleep/wake cycles. It responds via outputs to the posterior and anterior pituitary and the autonomic nervous system.

• Hormonal Regulation Pathway:

  • Hypothalamus: Secretes Gonadotropin-Releasing Hormone (GnRH).

  • Anterior Pituitary: GnRH stimulates the release of Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH).

  • Ovaries: FSH and LH stimulate the development of follicles, which produce estrogens and progesterone.

• Ovarian and Uterine Cycles:

  • Follicular Phase: Characterized by FSH-driven follicle growth and increasing estrogen levels.

  • Ovulation: Triggered by an LH surge around day $14$.

  • Luteal Phase: The corpus luteum forms, secreting progesterone and estrogen to prepare the uterine lining (stratum functionalis) for potential implantation.

  • Menses: If pregnancy does not occur, the corpus luteum regresses into the corpus albicans, progesterone drops, and the uterine lining sloughs off.

Functional Hypothalamic Anovulation/Amenorrhea (FHA)

• Epidemiology: Responsible for approximately $30\%$ of all cases of secondary amenorrhea.

• Clinical Definition: A diagnosis of exclusion. It is commonly seen in individuals characterized by:

  • Restricted food intake or low body weight/rapid weight loss.

  • Excessive exercise patterns.

  • Significant chronic stress (emotional or illness-induced).

  • Situations where energy intake is inadequate for the energy expended.

• Pathophysiology (Hypogonadotropic Hypogonadism):

  • Suppression of hypothalamic GnRH release leads to decreased amplitude and/or frequency of FSH and LH pulses.

  • The absence of gonadotropin stimulation prevents follicle formation in the ovaries.

  • Hormonal Results: Greatly decreased estradiol production, absence of LH surge, and failure to ovulate.

  • Endometrial Impact: Minimal endometrial proliferation occurs, resulting in amenorrhea or scant menses.

• Nutritional and Metabolic Signals:

  • Hypercortisolemia: Stress response leads to elevated cortisol, suppressing GnRH secretion.

  • Hypoleptinemia: Underweight status results in a drop in fat mass and lower leptin levels. This reduces hypothalamic kisspeptin and GnRH secretion.

  • Hyperghrelinemia: Underweight status increases ghrelin levels, which inhibits LH pulsatility.

• Relative Energy Deficiency in Sport (RED-S):

  • Formerly known as the Female Athletic Triad.

  • Components: (1) Low energy availability (+/- disordered eating), (2) Menstrual abnormalities (oligo- or amenorrhea), and (3) Bone density below expected age.

  • Prevalence: Seen in $60\%$ of elite middle- and long-distance athletes and $23\%$ of elite sprinters.

  • Bone Health Risks: Impaired bone accrual during adolescence and low bone density in adults. The hypo-estrogenic state nullifies the benefits of weight-bearing exercise for bone remodeling, increasing the risk of stress fractures. This is only partially reversible if menses resume.

• Stress-Induced FHA: Extreme chronic emotional stress increases secretion of CRH, ACTH, and cortisol. CRH inhibits GnRH pulse frequency directly, and cortisol suppresses both the hypothalamus and pituitary.

• Treatment Strategies:

  • Reverse the underlying cause (e.g., regain weight, treat eating disorders).

  • Adequate caloric intake and improved eating behaviors.

  • Decreased exercise when appropriate or increased calories to match expenditure.

  • Stress reduction and treatment of depression.

  • Estrogen Replacement: Consider transdermal estrogen at physiologic levels if no improvement occurs within $6-12$ months.

  • Supplementation with Calcium and Vitamin D.

Other Hypothalamic and Pituitary Disorders

• Thyroid Dysfunction:

  • Disturbs the menstrual cycle in roughly $23\%$ of hypothyroid and $22\%$ of hyperthyroid individuals.

  • Mechanism: Disrupts GnRH pulsatility. Elevated Thyroid-Releasing Hormone (TRH) in hypothyroidism can stimulate prolactin production. Hypothyroidism directly impairs folliculogenesis, corpus luteum function, and endometrial hemostasis.

• Congenital GnRH Deficiency (Kallman Syndrome): Features congenital GnRH deficiency accompanied by anosmia (loss of smell). Typically presents with delayed puberty.

• Hyperprolactinemia-Inducing Drugs: Medications that act as dopamine D2 receptor antagonists can cause elevated prolactin levels, which in turn suppresses GnRH.

  • Antipsychotics: Phenothiazines (e.g., chlorpromazine/Thorazine), Risperidone, and Butyrophenones (e.g., haloperidol/Haldol).

  • Gastric Motility/Antiemetics: Metoclopramide (Reglan) and Prochlorperazine (Compazine).

  • Antidepressants: TCAs, MAOIs, and SSRIs (mechanisms are less clear).

• Pituitary Lesions:

  • Prolactinoma: The most common pituitary tumor ($50\%$). Excessive prolactin suppresses GnRH and causes galactorrhea (bilateral milky discharge).

    • Treatment: Dopamine agonists like Bromocriptine (Parlodel) or Cabergoline (Dostinex). Resection for large tumors.

  • Stalk Disruption: Masses (e.g., craniopharyngioma, metastases, sarcoidosis, histiocytosis, hemochromatosis) can block the pathway of dopamine or GnRH from the hypothalamus to the anterior pituitary.

  • Sheehan’s Syndrome: Ischemic necrosis of the pituitary, often resulting from significant maternal hemorrhage during childbirth.

Polycystic Ovary Syndrome (PCOS/PMOS)

• Overview: The most common female endocrinopathy in developed countries, affecting $5-10\%$ of people of reproductive age. It is a syndrome of excess androgen production (usually ovarian, sometimes adrenal) leading to anovulation.

• New Name: Polyendocrine Metabolic Ovarian Syndrome (PMOS), emphasizing the metabolic components.

• Diagnostic Criteria (2018 International/Rotterdam Criteria): Must have at least $2$ of the following $3$ findings after excluding other causes (e.g., CAH, Cushing’s):

  1. Hyperandrogenism (clinical or biochemical).

  2. Ovulatory dysfunction (amenorrhea/oligomenorrhea).

  3. Polycystic ovary morphology on ultrasound (or specific AMH levels).

• Pathophysiology:

  • Increased GnRH pulse frequency favors LH synthesis over FSH.

  • LH Excess: Stimulates theca cells to produce more androgens (androstenedione and testosterone).

  • Relative FSH Deficiency: Limits the conversion of androgens to estrogens in granulosa cells via aromatase.

  • Insulin Resistance: Hyperinsulinemia stimulates theca cell androgen production and reduces Sex Hormone-Binding Globulin (SHBG) in the liver, increasing bioavailable (free) androgens. This is present in $50-80\%$ of U.S. patients.

• Clinical Presentations:

  • Hirsuitism: Terminal hair growth in male-type patterns (face, chest, back, thighs). Affects $65-75\%$ of patients. Prevalence varies by ethnicity (High: Middle Eastern, South Asian; Low: East/Southeast Asian).

  • Acne and Hair Loss: Pilotsebaceous unit stimulation and androgenic alopecia (seen in $20-35\%$).

  • Acanthosis Nigricans: Velvety, hyperpigmented skin on the neck or axillae, indicating insulin resistance.

  • Ovarian Morphology: "String of pearls" appearance (multiple cysts < 1\,cm). Note: Not everyone with polycystic ovaries has PCOS, and not everyone with PCOS has polycystic ovaries.

• Health Sequelae:

  • Infertility and Irregular Menses: Due to chronic anovulation.

  • Endometrial Cancer: $2.7 \times$ higher risk ($9\%$ lifetime risk) due to unopposed estrogen exposure.

  • Metabolic Risks: Type II DM ($2-5$ fold risk), atherogenic dyslipidemia ($70\%$), and cardiovascular disease.

• Treatment:

  • Lifestyle: Diet and exercise to reduce weight, insulin resistance, and testosterone.

  • Combined Hormonal Contraceptives (CHCs): Progestin inhibits LH release (dropping androgen production); estrogen increases SHBG (lowering free androgens). Provides endometrial protection.

  • Spironolactone ($25-100\,mg$ BID): Aldosterone antagonist and androgen receptor blocker. Requires $6$ months for effect. Potential teratogen (requires birth control).

  • Metformin: Second-line therapy; helps with insulin utilization but no longer primary for hyperandrogenemia or ovulation induction.

Primary Ovarian Insufficiency (POI)

• Definition: Formerly "premature menopause." Characterized by hypergonadotropic hypogonadism (elevated FSH and inactive/hypoactive gonads). Insufficiency implies some function may remain.

• Major Causes:

  1. Genetic: Most common recognized cause ($10-15\%$ identified).

     • Fragile X Premutation (FMR1): $55-200$ CGG repeats. $12-28\%$ experience menopause before age $40$.

     • Turner Syndrome ($45,X$): Occurs in $1$ in $2500-5000$ liveborn girls. Requires two intact X chromosomes to maintain oocytes.

  2. Autoimmune: Antibodies to theca cells, corpus luteum, or FSH receptors.

  3. Ovarian Toxins: Chemotherapy (alkylating agents are worst) and pelvic radiation.

  4. Infections/Other: Mumps or galactosemia.

• Turner Syndrome Characteristics: Short stature, webbed neck, sexual infantilism (streak gonads), cubitus valgus, broad "shield-like" chest, and possible cardiovascular ($20\%$) or renal abnormalities.

Case Study and Discussion

• Patient Presentation: A $17$-year-old G0 female with $3$ months of amenorrhea. Menses were regular from age $12$ until $6$ months ago. She recently joined a cross-country track team. Physical exam: $5\,ft\,4\,in$, weight $110\,lbs$.

• Diagnosis: The most likely cause is Functional Hypothalamic Anovulation (Amenorrhea), driven by high energy expenditure from daily track training and a relatively low body weight for her height.

• Clinical Pearl: The menstrual cycle should be considered a "vital sign." Abnormal uterine bleeding is a sign of many concerning etiologies and must be investigated.