Repetitive graded ACTH stimulation test for adrenal insufficiency

ACTH stimulation is useful in assessing the hypothalamo-pituitary-adrenal a xis. However, there is still some debate about the proper dose and interpre tation. We designed a new protocol using repetitive graded ACTH stimulation . Thirty-two patients with the diagnosis of adrenal insufficiency (AI) were studied. After taking samples for baseline ACTH and cortisol, 1 mu g fresh -prepared ACTH (Synacthen (1-24)) was injected intravenously, then 5, 50 an d 100 mu g at hourly interval. Cortisol responses were measured at 30, 60, 120, 180 and 240 min. The secondary Al group (26 subjects) had cortisol res ponses in between those of the control group (8 subjects) and the primary A l group (6 subjects). The minimal overlap between the secondary Al group an d the control group occurred at a 30-min cortisol response after 1 mu g ACT H stimulation, using 20 mu g/dl as the cut-off level. There was only one ex ception which showed an episodic release at 30 min. There were 5, 10 and 9 patients with secondary Al who responsed normally to 5, 50 and 100 mu g ACT H stimulation, respectively. Maximal cortisol increments of the primary Al group were all below 4 mu g/dl. Although there were 11 cases of secondary A l whose cortisol responses overlapped with those of primary Al, only two of them had a cortisol increment less than 4 mu g/dl. Our new protocol combin es the advantage of the low dose ACTH stimulation test, a sensitive method for detecting mild Al, and the ACTH infusion test, a longer test to mimic s urgical stress. (J. Endocrinol. Invest. 23: 163-169, 2000) (C) 2000, Editri ce Kurtis.