Professional and Linguistic Assessments Board (PLAB) Practice Exam

What is the screening test for acromegaly?

1. IGF-1

2. Growth hormone

3. Prolactin

4. Cortisol

The correct answer is: IGF-1

The screening test for acromegaly is indeed the measurement of Insulin-like Growth Factor 1 (IGF-1) levels. This is because acromegaly, which is often caused by excess growth hormone secretion, leads to elevated levels of IGF-1. This biomarker reflects the average levels of growth hormone over the preceding hours and is more stable than the growth hormone measurement itself, which can fluctuate significantly during the day. In practice, if a patient is suspected of having acromegaly due to signs like enlarged extremities, coarsened facial features, or other related symptoms, an elevated IGF-1 level would suggest the presence of growth hormone excess typically associated with acromegaly. Following an elevated IGF-1 result, further testing, including the oral glucose tolerance test (OGTT) to assess growth hormone response, may be conducted for confirmation. The other options, while important in different contexts, are not used specifically to screen for acromegaly. Growth hormone levels can vary greatly and do not provide reliable evidence of chronic excess. Prolactin levels are related more to conditions like prolactinoma, and cortisol is significant in diseases like Cushing's syndrome, but neither is indicative of ac