Polycystic Ovarian Syndrome for USMLE Step 3
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Polycystic Ovarian Syndrome (PCOS) for the USMLE Step 3 Exam
- Definition:
- PCOS is a common endocrine disorder in women of reproductive age, characterized by hyperandrogenism, menstrual irregularities, and polycystic ovaries. It is a leading cause of infertility and is associated with metabolic complications.
- Etiology and Pathophysiology:
- Genetic and Environmental Factors: PCOS is influenced by both genetic and environmental factors. The exact cause is unknown, but hormonal imbalance, particularly hyperandrogenism and insulin resistance, plays a central role.
- Hyperandrogenism: Androgen excess, originating mainly in the ovaries, leads to symptoms like hirsutism and acne and disrupts normal follicular development, causing anovulation.
- Insulin Resistance: Insulin resistance is common in PCOS, leading to hyperinsulinemia, which increases ovarian androgen production and further impairs follicle maturation.
Clinical Manifestations
- Menstrual Irregularities:
- Presents as oligomenorrhea (infrequent periods) or amenorrhea (absent periods) due to chronic anovulation.
- Hyperandrogenism:
- Hirsutism: Excess hair growth on the face, chest, and abdomen.
- Acne and Seborrhea: Androgens stimulate sebaceous glands, leading to acne and oily skin.
- Alopecia: Male-pattern hair loss in more severe cases.
- Metabolic Disturbances:
- Insulin Resistance and Obesity: Common in PCOS and associated with central adiposity, leading to increased risk of type 2 diabetes.
- Dyslipidemia: Includes elevated LDL cholesterol and triglycerides and reduced HDL cholesterol, contributing to cardiovascular risk.
- Infertility:
- Chronic anovulation makes PCOS a common cause of infertility; even in ovulatory cycles, impaired endometrial receptivity may further reduce fertility.
- Acanthosis Nigricans:
- Dark, thickened patches of skin, often seen in the neck, axillae, and groin, associated with insulin resistance.
Diagnostic Criteria
- Rotterdam Criteria:
- Diagnosis requires two of the following three features, after excluding other causes of hyperandrogenism:
- Oligo- or Anovulation: Infrequent or absent menstrual cycles.
- Hyperandrogenism: Clinical (e.g., hirsutism) or biochemical (elevated serum androgens) evidence.
- Polycystic Ovaries on Ultrasound: ≥12 follicles in each ovary (2–9 mm) or increased ovarian volume (>10 mL).
- Exclusion of Other Conditions:
- Hyperprolactinemia, hypothyroidism, and androgen-secreting tumors can mimic PCOS and should be ruled out.
- Congenital Adrenal Hyperplasia (CAH): Excluded by measuring 17-hydroxyprogesterone.
Laboratory Evaluation
- Hormonal Assessment:
- Total and Free Testosterone: Often elevated, indicating hyperandrogenism.
- LH and FSH: An elevated LH/FSH ratio (>2:1) may be present but is not diagnostic.
- Estradiol: Typically normal or mildly elevated due to continuous estrogen production without ovulation.
- Metabolic Screening:
- Oral Glucose Tolerance Test (OGTT): Recommended to assess glucose tolerance due to high risk of diabetes.
- Lipid Profile: To evaluate dyslipidemia, which is common in PCOS.
Management
Lifestyle and Weight Management
- Weight Loss: A 5-10% reduction in body weight can restore ovulation and improve metabolic health.
- Diet and Exercise: A low-glycemic index diet and regular physical activity enhance insulin sensitivity.
Pharmacologic Treatments
- Hormonal Contraceptives:
- Combined Oral Contraceptives (COCs): First-line for menstrual irregularities and hyperandrogenic symptoms. They regulate cycles, reduce androgens, and prevent endometrial hyperplasia.
- Progestin-Only Options: Suitable for women who cannot take estrogen, helping regulate menstruation and reduce hyperplasia risk.
- Anti-Androgens:
- Spironolactone: Used for hirsutism and acne; blocks androgen receptors and inhibits androgen production.
- Finasteride: Reduces the conversion of testosterone to DHT, helping with androgenic symptoms.
- Metformin:
- Improves insulin sensitivity, reduces glucose levels, and may restore ovulation. Commonly used alongside lifestyle interventions for metabolic management.
- Ovulation Induction:
- Letrozole: Preferred first-line for inducing ovulation in infertility cases; inhibits aromatase, increasing FSH levels.
- Clomiphene Citrate: An alternative for inducing ovulation, though less effective than letrozole in PCOS.
Key Points
- PCOS is a common endocrine disorder in reproductive-age women, characterized by hyperandrogenism, irregular menstruation, and polycystic ovaries.
- Clinical Features include menstrual irregularities, hyperandrogenic symptoms (hirsutism, acne), metabolic abnormalities (insulin resistance, obesity), and infertility.
- Diagnosis follows the Rotterdam criteria, requiring two of three findings (oligo/anovulation, hyperandrogenism, and polycystic ovaries) after ruling out other potential causes.
- Management includes lifestyle modification, hormonal therapy (COCs), anti-androgens (e.g., spironolactone), and ovulation induction (letrozole) for infertility.
- Long-Term Complications: Increased risk of type 2 diabetes, cardiovascular disease, and endometrial hyperplasia or cancer due to chronic anovulation.