Biochemical discrepancies in the evaluation of the somatotroph axis: Elevated GH or IGF-1 levels do not always diagnose acromegaly

The most frequent diagnosis underlying the finding of an elevated growth hormone (GH) and insulin-like growth factor-1 (IGF-1) is acromegaly due to a GH-secreting pituitary tumour. However, GH and IGF-1 levels can be discordant in patients with acromegaly due to early or partially treated disease, or there might be another cause of high GH or high IGF-1 unrelated to acromegaly, such as pre-analytical and technical pitfalls, physiological circumstances and pathological conditions. High GH and normal or low serum IGF-1, or alternatively, normal GH with elevated serum IGF-1, should be carefully assessed to avoid misinterpreting the activity of acromegaly or misdiagnosing a patient with acromegaly. We summarise here these biochemical discrepancies in the evaluation of the somatotroph axis.