**Core Concept**
Carpal tunnel syndrome (CTS) is a clinical entity characterized by median nerve compression at the wrist level, leading to symptoms like paresthesia, numbness, and weakness in the hand. Endocrinal causes of CTS involve hormonal imbalances affecting nerve conduction and muscle size.

**Why the Correct Answer is Right**
The correct answer involves understanding the pathophysiology of endocrinal causes of CTS. Thyrotoxicosis, hypothyroidism, and hyperparathyroidism can cause CTS due to their effects on muscle and nerve function. For instance, thyrotoxicosis can lead to muscle swelling, compressing the median nerve, while hypothyroidism can cause nerve conduction slowing. Hyperparathyroidism can cause hypercalcemia, leading to nerve damage and swelling.

**Why Each Wrong Option is Incorrect**
* **Option A:** Incorrect because acromegaly is a condition characterized by excessive growth hormone production, leading to soft tissue and bone enlargement, which can cause CTS. However, this option is not listed, so we will move on to the actual options.
* **Option B:** Incorrect because hypopituitarism is a condition characterized by insufficient hormone production, which is not typically associated with CTS.
* **Option C:** Incorrect because Cushing's syndrome is a condition characterized by excessive cortisol production, which can lead to muscle and fat accumulation, causing nerve compression and CTS.

**Clinical Pearl / High-Yield Fact**
When evaluating patients with CTS, it's essential to consider endocrinal causes, especially in patients with unexplained symptoms or those with a history of hormonal imbalances.

**Correct Answer: B. Hypopituitarism.