How do I interpret serum IGF-1 levels in the context of suspected acromegaly, and what are the next steps if levels are elevated?

In the context of suspected acromegaly, serum insulin-like growth factor 1 (IGF-1) levels are considered a crucial component of biochemical assessment (Freda, 2003). Elevated IGF-1 levels are indicative of increased growth hormone (GH) secretion and are a primary diagnostic marker for acromegaly (Freda, 2003). The interpretation of IGF-1 levels should take into account age- and sex-matched reference ranges, as IGF-1 levels naturally decline with age (Freda, 2003).

If serum IGF-1 levels are found to be elevated, the appropriate next step in biochemical assessment is typically to confirm autonomous GH secretion (Freda, 2003). This is commonly achieved through an oral glucose tolerance test (OGTT) with serial GH measurements (Freda, 2003). A failure of GH levels to suppress below a certain threshold (e.g., 1.0 µg/L or 0.4 µg/L depending on the assay sensitivity) during an OGTT, in conjunction with elevated IGF-1, confirms the diagnosis of acromegaly (Freda, 2003). It is important to note that the provided UK guidelines (NG230, NG243, NG232, NG132) do not specifically cover the assessment and management of acromegaly.