**Question:** All of the following drugs can cause gynaecomastia except

A. Progesterone
B. Testosterone
C. Alprazolam
D. Tamoxifen

**Core Concept:**
Gynaecomastia is a condition characterized by enlarged breast tissue in males, often due to hormonal imbalances. Testosterone is a male sex hormone that typically contributes to male secondary sexual characteristics and is responsible for reducing breast tissue in males. Progesterone is another hormone, but in contrast to testosterone, it is involved in female reproductive processes and is not associated with reducing male breast tissue. Alprazolam and Tamoxifen are medications with different mechanisms and are not primarily responsible for causing gynaecomastia.

**Why the Correct Answer is Right:**
Drugs that cause gynaecomastia usually interfere with the balance between testosterone and progesterone, leading to increased breast tissue in males. Progesterone, being primarily involved in female reproductive processes, does not contribute to the maintenance of male breast tissue and is therefore less likely to cause gynaecomastia. Testosterone, on the other hand, is the primary hormone responsible for maintaining normal male breast tissue and reducing the risk of gynaecomastia.

**Why Each Wrong Option is Incorrect:**
A. Progesterone: As mentioned earlier, progesterone is primarily involved in female reproductive processes and does not regulate male breast tissue, making it an unlikely cause of gynaecomastia.
B. Testosterone: Testosterone is a male sex hormone responsible for maintaining normal male breast tissue and reducing the risk of gynaecomastia.
C. Alprazolam: Alprazolam is a benzodiazepine used for treating anxiety disorders and panic disorders. Although it can cause gynecomastia as an adverse effect, it is not primarily responsible for causing gynaecomastia.
D. Tamoxifen: Tamoxifen is an antineoplastic agent used to treat breast cancer by blocking estrogen action. While it can cause gynecomastia, it is not primarily responsible for causing gynaecomastia.

**Clinical Pearl:**
Understanding the role of hormones like testosterone and progesterone in maintaining male breast tissue and their association with gynaecomastia is essential for clinical practice. Awareness of the potential side effects of drugs like alprazolam and tamoxifen helps in identifying potential causes of gynaecomastia in patients taking these medications.