## **Core Concept**
Gynaecomastia is a condition characterized by the enlargement of breast tissue in males, often caused by an imbalance of sex hormones, specifically an increase in estrogen relative to testosterone. Certain medications can disrupt this balance, leading to gynaecomastia.

## **Why the Correct Answer is Right**
Spironolactone, an aldosterone antagonist used primarily in the treatment of heart failure and hypertension, is known to cause gynaecomastia as a side effect due to its anti-androgenic properties. It competes with androgens for receptors, potentially leading to hormonal imbalances that cause breast tissue growth. Similarly, drugs like ketoconazole and metoclopramide can also cause gynaecomastia through different mechanisms, such as inhibiting testosterone synthesis or affecting dopamine receptors which influence prolactin levels.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Spironolactone is a well-known cause of gynaecomastia due to its anti-androgen effects.
- **Option B:** Ketoconazole can cause gynaecomastia by inhibiting the synthesis of testosterone.
- **Option C:** Metoclopramide can lead to gynaecomastia indirectly through its effect on prolactin levels.
- **Option D:** Atenolol, a beta-blocker used in the management of hypertension and certain heart conditions, is not commonly associated with gynaecomastia as a side effect.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that gynaecomastia can be caused by a variety of drugs, including spironolactone, certain antipsychotics, and some chemotherapeutic agents. When evaluating gynaecomastia, it's crucial to take a thorough drug history.

## **Correct Answer:** D. Atenolol