**Core Concept**
The enlargement of a pituitary tumor after adrenalectomy is a rare but serious complication that occurs due to the removal of both adrenal glands, leading to an increase in adrenocorticotropic hormone (ACTH) production and subsequent growth of the pituitary tumor.

**Why the Correct Answer is Right**
Nelson's syndrome is a condition characterized by the rapid growth of a pituitary tumor, specifically a corticotroph adenoma, following bilateral adrenalectomy. This occurs because the removal of the adrenal glands eliminates the negative feedback mechanism that regulates ACTH production, allowing the pituitary tumor to grow unchecked. The resulting tumor can produce large amounts of ACTH, leading to Cushing's disease-like symptoms. The growth of the tumor can be aggressive and may require surgical intervention.

**Why Each Wrong Option is Incorrect**
* **Option B:** Steel-Richardson-Olszewski syndrome, also known as progressive supranuclear palsy, is a neurodegenerative disorder that affects movement and balance, but it is not related to pituitary tumor growth after adrenalectomy.
* **Option C:** Hamman-Rich syndrome, also known as acute interstitial pneumonia, is a rare and severe lung disease that is not associated with pituitary tumors or adrenalectomy.
* **Option D:** Job's syndrome, also known as hyperimmunoglobulin E syndrome, is a rare genetic disorder characterized by recurrent infections and elevated levels of IgE, but it is not related to pituitary tumor growth after adrenalectomy.

**Clinical Pearl / High-Yield Fact**
It is essential for surgeons to be aware of the potential complications of adrenalectomy, including Nelson's syndrome, and to closely monitor patients for signs of pituitary tumor growth after surgery.

**✓ Correct Answer: A. Nelson's syndrome**