Which of the following is the most common cause of anovulation in women of reproductive age?

Explanation

## Anovulation and PCOS **Key Point:** Polycystic ovary syndrome (PCOS) accounts for approximately 70–80% of anovulatory infertility cases in women of reproductive age. ### Pathophysiology of PCOS 1. **Insulin resistance** → hyperinsulinemia 2. **Excess androgen production** → suppression of FSH, disruption of follicular maturation 3. **Abnormal GnRH pulsatility** → elevated LH:FSH ratio 4. **Anovulation** → absence of ovulation and corpus luteum formation ### Clinical Features of PCOS | Feature | Prevalence | | --- | --- | | Oligomenorrhea/amenorrhea | 70–80% | | Hirsutism | 60–80% | | Acne | 20–30% | | Obesity | 40–50% | | Infertility | 20–40% | **High-Yield:** PCOS is the leading cause of anovulatory infertility; diagnosis requires Rotterdam criteria (2 of 3: oligo-/anovulation, hyperandrogenism, polycystic ovarian morphology on ultrasound). **Clinical Pearl:** Even lean women with PCOS may have insulin resistance and anovulation; BMI alone does not exclude the diagnosis. ### Other Causes of Anovulation (Less Common) - **Hyperprolactinemia** (5–10% of anovulatory cases): inhibits GnRH pulsatility - **Thyroid dysfunction** (2–5%): affects metabolism and gonadotropin secretion - **Premature ovarian failure** (1–2%): destruction of follicular reserve [cite:Textbook of Obstetrics & Gynaecology (Hiralal Konar) Ch 15]