**Core Concept**
Hirsutism in females is a condition characterized by excessive growth of terminal hair in a male-like pattern, often due to an excess of androgens. This condition can be caused by various factors, including hormonal imbalances, genetic disorders, and certain medical conditions.

**Why the Correct Answer is Right**
The most common cause of hirsutism in females is polycystic ovary syndrome (PCOS). PCOS is a complex endocrine disorder that affects ovulation and hormone production, leading to an excess of androgens, which in turn causes hirsutism. The pathophysiology of PCOS involves insulin resistance, hyperinsulinemia, and an imbalance of androgen production, which is often due to an abnormality in the hypothalamic-pituitary-ovarian axis.

**Why Each Wrong Option is Incorrect**
**Option A:** Congenital adrenal hyperplasia is a genetic disorder that can cause an excess of androgens, but it is not the most common cause of hirsutism in females.
**Option B:** Adrenal tumors can cause an excess of androgens, but they are relatively rare compared to PCOS.
**Option C:** Idiopathic hirsutism is a condition where the cause of hirsutism is unknown, but it is not a specific medical condition that can be diagnosed.

**Clinical Pearl / High-Yield Fact**
PCOS is the most common endocrine disorder in women of reproductive age and is associated with an increased risk of metabolic syndrome, type 2 diabetes, and cardiovascular disease.

**Correct Answer:** A. PCOS.