We describe a patient with macroprolactinoma and discrepant insulin-like growth factor (IGF-1) concentration (elevated) and growth hormone (GH) values during a 75 g oral glucose tolerance test (normal), that were measured to evaluate the co-secretion of GH by tumor. With the bromocriptin use, the patient achieved normalization of prolactin, but persisted with high levels of IGF1, suggesting to be subclinical acromegaly. After the development of new more sensitive GH assays, cases of discrepant GH and IGF-1 results have been observed and taken to some authors to suggest that GH nadir concentration during 75 g OGTT used to acromegaly diagnosis and treatment could be lower than values considered currently normal. Thus, if this is confirmed, subclinical and oligosymptomatic acromegaly cases could have earlier diagnoses.
Acromegaly; Prolactinoma; Growth hormone; IGF-1
