**Question:** Commonest cause of anovulatory infertility -

A. Polycystic Ovary Syndrome (PCOS)
B. Hypothyroidism
C. Ovarian torsion
D. Polycystic Ovary Syndrome and Hypothyroidism

**Correct Answer: A. Polycystic Ovary Syndrome (PCOS)**

**Core Concept:**
Anovulatory infertility refers to a condition where ovulation does not occur in females seeking pregnancy. The primary cause can be attributed to hormonal imbalances, anatomical abnormalities, or both. Among these causes, Polycystic Ovary Syndrome (PCOS) is the most common.

**Why the Correct Answer is Right:**
PCOS is a common endocrine disorder affecting women of reproductive age. It is characterized by chronic anovulation, hyperandrogenism, and polycystic ovaries on ultrasound examination. The primary hormonal abnormality in PCOS is hyperinsulinemia, leading to elevated luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels, with a disproportionate LH:FSH ratio. The elevated LH stimulates ovarian theca cells to produce excessive amounts of androgens, which in turn suppresses follicle development and ovulation.

**Why Each Wrong Option is Incorrect:**

**B. Hypothyroidism**
Hypothyroidism is a thyroid hormone deficiency resulting in decreased thyroid-stimulating hormone (TSH) and elevated thyroid hormones (T4, T3). It may lead to anovulation due to impaired gonadotropin secretion from the pituitary gland, but PCOS is the more common cause of anovulation in women of reproductive age.

**C. Ovarian torsion**
Ovarian torsion occurs when the ovary twists on its pedicle, disrupting blood supply and causing acute abdominal pain. This is a surgical emergency, not a cause of anovulation in routine clinical practice.

**D. Polycystic Ovary Syndrome and Hypothyroidism**
While both PCOS and hypothyroidism can contribute to anovulation, PCOS is the primary cause due to hormonal imbalances, while hypothyroidism is a separate entity with distinct clinical features and management.

**Why the Correct Answer is Right:**
The correct answer is A. Polycystic Ovary Syndrome (PCOS), as it is the most common cause of chronic anovulation in women of reproductive age. PCOS affects approximately 10-20% of women and is the primary cause of anovulatory infertility. The underlying hormonal imbalance leads to chronic anovulation, hyperandrogenism, and polycystic ovaries on ultrasound examination.

**Clinical Pearls:**
1. **Oligomenorrhea or amenorrhea**: PCOS is often associated with irregular menstrual cycles (oligomenorrhea) or absence of menstrual periods (amenorrhea).
2. **Hyperandrogenism**: Elevated androgen levels lead to clinical signs such