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Acromegaly is a rare pituitary disorder characterized by the inappropriate secretion of growth hormone (GH) by a pituitary adenoma in most cases. Diagnostic criteria of acromegaly have significantly changed over the last 25 years, providing different cut-offs of serum GH levels both in basal conditions and after glucose inhibition. Historically, due to several analytical limitations in GH and insulin-like growth factor I (IGF-I) assays, the confirmation of clinically suspected acromegaly was primarily based on dynamic tests involving the administration of substances known to acutely and physiologically modulate GH secretion. In some cases, paradoxical GH responses have been observed during these dynamic tests. The oral glucose tolerance test (OGTT), performed with the administration of 75 g of glucose, is currently the only dynamic test recommended by clinical guidelines in acromegaly. Initially, a paradoxical response during OGTT was defined as the failure of GH suppression following glucose exposure. More recently, this definition has evolved with the introduction of additional criteria, including the percentage increase in GH levels, the GH ratio, and temporal parameters. Over time, the GH response during OGTT has been used for different purposes. Initially, it served as a diagnostic tool; however, the most recent consensus statements recognize its role as a prognostic indicator of long-term remission following neurosurgical treatment. Therefore, considering the predictive value of certain dynamic tests in assessing treatment response in acromegaly, this review aims to provide a comprehensive overview of the evolution of dynamic testing in acromegaly, with a specific focus on tests associated with paradoxical GH responses.
Marinis et al. (Tue,) studied this question.