**Core Concept**
Acromegaly is a disorder characterized by excessive growth hormone (GH) production, leading to various systemic manifestations. Screening for acromegaly involves identifying patients with abnormal GH levels, typically through a simple and non-invasive test.

**Why the Correct Answer is Right**
The correct screening test for acromegaly is the insulin tolerance test (ITT). During ITT, insulin is administered to lower blood glucose levels, triggering a natural response to increase GH production. In patients with acromegaly, the GH response is exaggerated due to the underlying GH-producing adenoma. The ITT measures the GH level after glucose suppression, helping to diagnose GH excess. This test is particularly useful because it assesses the body's ability to suppress GH production in response to decreased glucose levels.

**Why Each Wrong Option is Incorrect**
**Option A:** Random GH measurement is not a reliable screening test for acromegaly because GH levels can fluctuate naturally throughout the day. This makes it challenging to determine a specific threshold for abnormality.
**Option B:** The oral glucose tolerance test (OGTT) can be used to diagnose acromegaly, but it is not the preferred initial screening test. OGTT measures GH levels after glucose intake, but it can be influenced by various factors, including the dose and timing of glucose administration.
**Option C:** The growth hormone-releasing hormone (GHRH) test is used to diagnose GH deficiency, not acromegaly. During this test, GHRH is administered to stimulate GH production, and the response is measured. In patients with GH deficiency, the GH response is blunted.

**Clinical Pearl / High-Yield Fact**
Remember that acromegaly is often diagnosed incidentally during routine health exams or when investigating symptoms like joint pain, sleep apnea, or abnormal facial features. A high index of suspicion is essential, especially in patients with a family history of pituitary tumors or those with known conditions like hypopituitarism.

**Correct Answer:** C. Oral glucose tolerance test (OGTT)