**Core Concept**
Gynaecomastia refers to the benign enlargement of breast tissue in males, often resulting from an imbalance between estrogen and androgen levels. This condition can be caused by various factors, including hormonal changes, medications, and underlying medical conditions.

**Why the Correct Answer is Right**
The correct answer is related to the increased levels of estrogen relative to androgen levels. Estrogen promotes the growth of breast tissue, whereas androgen inhibits it. When androgen levels decrease or estrogen levels increase, it can lead to the development of gynaecomastia. This imbalance can be caused by conditions such as Klinefelter syndrome, testicular cancer, liver disease, or the use of certain medications like spironolactone.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not directly relate to the hormonal imbalance causing gynaecomastia. While obesity is a risk factor for various health conditions, it is not a primary cause of gynaecomastia.
* **Option B:** This option is incorrect because it is not a typical cause of gynaecomastia. While certain medications can cause gynaecomastia, this option does not specify a medication that is commonly associated with the condition.
* **Option D:** This option is incorrect because it is not a direct cause of gynaecomastia. While certain medical conditions can increase estrogen levels, this option does not specify a condition that is commonly associated with gynaecomastia.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that gynaecomastia can be a sign of an underlying medical condition, such as hypogonadism or testicular cancer. A thorough medical history and physical examination are essential in diagnosing the underlying cause of gynaecomastia.

**Correct Answer: C. Increased levels of estrogen relative to androgen levels.**