[Growth hormone (GH) and IGF-I assays: methodological aspects and its implications in acromegaly diagnosis and follow-up]

Growth hormone quantification in serum is essential for confirming or ruling out its excess. The absence of clinical criteria sufficiently sensitive to evaluate the treatment success enables GH as the key diagnostic procedure and for that, its measurements must be done in a reliable way and must allow uniform interpretation. Several different biochemical criteria for remission have been suggested in the past, including a random GH measurement less than 2.5 microg/l, mean GH value from a day curve less than 2.5 microg/l, nadir GH value after an oral glucose tolerance test (OGGT) less than 1.0 microg/l and a normal age-related IGF-I level. The importance of adequate treatment is highlighted by data indicating that lowering GH levels to less than 2.5 microg/l reverses the premature mortality of acromegaly. With the advances of ultrasensitive assays for GH measurement, strictest remission criteria to determine remission or cure were necessary. In this review, we describe the changes of assay methodology and its consequences in serum GH results and cut off point values to define activity and remission of acromegaly.