Gynaecomastia is a side effect of all, EXCEPT :
**Core Concept**
Gynaecomastia is a benign enlargement of breast tissue in males, often caused by an imbalance of sex hormones, specifically an increase in estrogen relative to testosterone. This condition can be triggered by various medications, including some that affect hormone levels or block androgen receptors.
**Why the Correct Answer is Right**
The correct answer is related to a medication that does not cause an imbalance of sex hormones or block androgen receptors. The pathophysiology of gynaecomastia involves the estrogen-to-testosterone ratio, which is often disrupted by estrogens, anti-androgens, or substances that affect the hypothalamic-pituitary-gonadal axis.
**Why Each Wrong Option is Incorrect**
**Option A:** Spironolactone is a potassium-sparing diuretic that blocks the effects of aldosterone and also has anti-androgen properties, leading to gynaecomastia as a side effect.
**Option B:** Digoxin, a cardiac glycoside used in heart failure and atrial fibrillation, can increase the risk of gynaecomastia due to its estrogen-like effects.
**Option C:** Flutamide is an anti-androgen used in the treatment of prostate cancer, which can cause gynaecomastia as a side effect.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that gynaecomastia can also be caused by non-pharmacological factors, such as Klinefelter syndrome, liver disease, or testicular disorders, and that a thorough medical history and physical examination are necessary to determine the underlying cause.
**Correct Answer: D.**