Hexarelin as a test of pituitary reserve in patients with pituitary disease

BACKGROUND The insulin tolerance test (ITT) is the reference standard for the diagnosis of cortisol and growth hormone (GH) deficiency, but problems have occurred in small children in inexperienced hands and it is contraindicated in patients with cardiac disease and epilepsy. Hexarelin is a growth hormone‐releasing peptide with GH‐, ACTH/cortisol‐ and prolactin‐releasing effects which involve both hypothalamic and direct pituitary mechanisms. We therefore investigated whether it could be used to test GH and ACTH/cortisol reserve in patients with pituitary disease. METHODS AND SUBJECTS The changes in GH and cortisol in response to insulin‐induced hypoglycaemia (intravenous human Actrapid 0.15 IU/kg) and hexarelin (2 μg/kg) in 19 patients with possible pituitary disease (5 males, mean age 39 years, range 21–70) were compared. The patients' responses during the hexarelin test were also compared to normal ranges of GH and cortisol responses established in healthy volunteers following hexarelin administration. RESULTS AND DISCUSSION GH peak levels were significantly higher after hexarelin than after hypoglycaemia (mean ± SEM; 67.1 ± 16 vs. 26.9 ± 6.8 mU/l respectively; P