**Core Concept**
Cushing's syndrome is a hormonal disorder caused by excess levels of cortisol in the body, often due to an adrenal tumor. The goal of treatment is to reduce cortisol production to alleviate symptoms.

**Why the Correct Answer is Right**
The correct answer is **Mitotane (Lysodren)**. Mitotane is a medication specifically used to treat Cushing's syndrome by inhibiting the production of cortisol in the adrenal gland. It works by inducing apoptosis in the adrenal cortical cells, thereby reducing cortisol production. **Mitotane** is particularly useful in cases where the adrenal tumor cannot be surgically removed.

**Why Each Wrong Option is Incorrect**
**Option A:** **Ketoconazole** is an antifungal medication that can also inhibit cortisol production by blocking the enzyme 11β-hydroxylase. However, it is not the first-line treatment for adrenal tumors causing Cushing's syndrome. **Option B:** **Labetalol** is a beta-blocker used to manage hypertension and tachycardia, but it does not address the underlying cause of Cushing's syndrome. **Option C:** **Metyrapone** is a medication that inhibits cortisol production, but it is more commonly used in cases of Cushing's syndrome due to excessive ACTH production, not adrenal tumors.

**Clinical Pearl / High-Yield Fact**
Mitotane can have significant side effects, including adrenal insufficiency, nausea, and fatigue. It is essential to monitor cortisol levels and adjust the dosage accordingly to avoid adrenal crisis.

**Correct Answer:** C. Metyrapone