Which diagnostic test is performed first to check for Acromegaly?

The most appropriate initial diagnostic test to check for acromegaly is the measurement of IGF-1 levels. Acromegaly is typically caused by excessive growth hormone (GH) production, often from a pituitary adenoma. The reason IGF-1 testing is favored is that IGF-1 is a hormone that is stimulated by growth hormone and reflects its secretion in a stable manner throughout the day, making it a reliable indicator of growth hormone activity.

Measuring IGF-1 levels is a straightforward and effective first step. If IGF-1 levels are elevated, it suggests the presence of excess growth hormone, warranting further testing, such as confirming growth hormone levels through a glucose tolerance test or imaging studies like MRI or CT.

Imaging tests like MRI and CT are usually performed later to visualize the pituitary gland and identify any tumors but are not the first line in diagnosis. The glucose tolerance test can help confirm pathological GH secretion, but it is also not performed first because it is more invasive and requires fasting. Thus, measuring IGF-1 levels is the most efficient and informative initial step in diagnosing acromegaly.