Comparison of a combination test (1 µg ACTH test plus glucagon test) versus 1 µg ACTH test and glucagon test in the evaluation of the hypothalamic-pituitary-adrenal axis in patients with pituitary disorders

ABSTRACT Objective To investigate whether a combination of the low-dose (1 µg) adrenocorticotropin (ACTH) stimulation test and glucagon stimulation test (GST) could overcome the problem of equivocal results with the GST or ACTH test alone in patients with pituitary disorders. Subjects and methods The study included 41 adult patients with pituitary disorders and 20 healthy subjects who underwent evaluation of cortisol response to ACTH, GST, and a combination of both tests. Blood samples for cortisol measurement were obtained at baseline and 30, 60, 90, and 120 minutes after intravenous administration of ACTH 1 μg and 90, 120, 150, 180, 210, and 240 minutes after subcutaneous injection of glucagon 1 mg. The combination test was performed by injecting ACTH 1 µg at the 180-minute time point of the GST, with blood samples for cortisol measurement obtained at 210 and 240 minutes. Results Overall, 28 patients with normal cortisol response to both tests also had a normal cortisol response to the combination test. Ten patients with adrenal insufficiency in both tests also had adrenal insufficiency in the combination test, including a patient who had a peak cortisol value of 12.4 µg/dL (which is the cutoff value for the combination test). Two patients with adrenal insufficiency in the ACTH stimulation test and one patient with adrenal insufficiency in the GST had normal cortisol responses to the combination test. Conclusion By using an appropriate cutoff value, the combination test may offer additional information in patients with equivocal results in the GST and ACTH stimulation test.

Cortisol plasmático basal matinal como predictor de indemnidad del eje hipotálamo hipófisis suprarrenal / Basal morning serum cortisol for the assessment of hypothalamic, pituitary adrenal axis function

The study of hypothalamic, pituitary adrenal axis function requires complex tests. However, themeasurement of basal morning serum cortisol levels may be a simple measure to evaluate this axis. AIM: To determine if an isolated morning measurement of basal serum cortisol levels in the absence of stress, may predict the indemnity of the hypothalamic, pituitary adrenal axis. MATERIAL AND METHODS: Morning cortisol levels in the basal period and 30 minutes after the injection of 50 ug ACTH were measured in 76 patients with a mean age of 52 years (48 females), operated of a pituitary tumor, without cushing syndrome and not using steroids or oral estrogens. Twenty healthy volunteers with a mean age of 30 years (11 males) were studied as controls. In this last group, the lower limit of normal stimulated cortisol levels was defined as the mean value less two standard deviations and corresponded to 17 ug/dL. RESULTS: Based on stimulated cortisol levels, 15 percent of operated patients had a hypothalamic, pituitary adrenal axis dysfunction. Using cut-off levels of less than 5, 7.5 and 10 ug/dL, basal cortisol levels had a sensitivity for the diagnosis of hypothalamic, pituitaryadrenal axis dysfunction of 64, 81 and 100 percent, respectively. The figures were 100, 95 and 66 percent for specificity respectively, 100, 75 and 34 percent for positive predictive value and 94, 97 and 100 percent for negative predictive value. CONCLUSIONS: A basal morning cortisol value over 10 ug/dL discards the presence of hypothalamic, pituitary adrenal axis dysfunction and a value lower than 5 ug/dL confirmed alteration in all of the cases.