A Comparison between the 1-μg Adrenocorticotropin (ACTH) Test, the Short ACTH (250 μg) Test, and the Insulin Tolerance Test in the Assessment of Hypothalamo-Pituitary-Adrenal Axis Immediately after Pituitary Surgery

Abstract

The short ACTH stimulation test is an easy, reliable, and extensively used test in the assessment of the hypothalamo-pituitary-adrenal (HPA) axis. However, its use immediately after pituitary surgery is a matter of debate. The insulin tolerance test (ITT) is the gold standard in the evaluation of the HPA axis, but it is not always without side effects and may be unpleasant early after pituitary surgery. Our aim was to investigate the value of the 1-microg ACTH test in the assessment of the HPA axis early after pituitary surgery. We also aimed to determine the value of the 1-microg and 250-microg ACTH tests and the ITT in the estimation of HPA axis status after 3 months postoperatively. Nineteen patients subjected to pituitary tumor surgery were included in the study, and the ITT and the 1-microg and 250-microg ACTH tests were performed between the 4th and 11th days of surgery. The tests were repeated at the first month in 3 patients with subnormal peak cortisol responses (454, 125, and 301 nmol/L) and in 18 patients at the third month postoperatively. ACTH stimulation tests were performed by using 1 microg and 250 microg ACTH iv as a bolus injection, and blood samples were drawn at 0, 30, and 60 min for measurement of serum cortisol levels. The ITT was performed by using iv regular insulin, and serum glucose and cortisol levels were measured. The 1-microg and 250-microg ACTH stimulation tests and the ITT were performed consecutively. At least 48 h were allowed between each test. A peak serum cortisol level of 550 nmol/L or greater was considered as a normal response for both the ITT and the ACTH tests. The serum cortisol level was measured by RIA using commercial kits. Serum glucose was determined by glucose oxidase method. There were correlations between the peak cortisol response to the ITT and the 1-microg ACTH test (r = 0.39, P < 0.05) in the early postoperative period. No correlation was found between the ITT and the 250-microg ACTH test responses. In the early postoperative period, two patients showed normal cortisol responses (> or =550 nmol/L) to the 1-microg ACTH test and five patients showed normal cortisol responses to the 250-microg ACTH test among the six patients with subnormal cortisol responses to the ITT. Three patients with subnormal cortisol responses to ITT and baseline cortisol values less than 240 nmol/L showed normal HPA axis at the end of the first month. In the late postoperative period, at the third month, all the patients showed normal HPA axis. In the early postoperative period of pituitary surgery, the 1-microg ACTH test results are more concordant than the 250-microg ACTH test in comparison with the ITT. Our results also indicate that HPA axis dysfunction shown by ACTH stimulation tests and the ITT in early postoperative period may be normalized 1-3 months after surgery. For this reason, we think that dynamic tests including the ITT may not be useful early after pituitary surgery.

A comparison of low‐dose ACTH, glucagon stimulation and insulin tolerance test in patients with pituitary disorders

“…21 ACTH directly stimulates the adrenal glands and if performed with low doses, it has been shown to be well correlated with ITT. 16,22 Glucagon is thought to have similar or less power than ITT in the stimulation of cortisol production. 11,23 We have previously shown that GST and low-dose ACTH were less potent than standard-dose ACTH in the stimulation of the HPA axis in healthy adults.…”

“…Low-dose ACTH stimulation test was suggested to be a sensitive and easy alternative of ITT. [14][15][16][17] ITT was compared with GST in patients following pituitary surgery, and the authors found that a peak cortisol response of <277 nM to glucagon was 72% sensitive and >95% specific in the diagnosis of adrenal insufficiency. 11 In the present study, we compared, for the first time, ITT, low-dose ACTH and GSTs with each other in the evaluation of HPA and GH-IGF-1 axes in patients with pituitary disorders and evaluated the repeatability of all three tests.…”

The Role of Morning Basal Serum Cortisol in Assessment of Hypothalamic Pituitary-Adrenal Axis

“…e standard dose ACTH stimulation test was used exclusively in this study as previous studies have established it as an e ective alternative to the more cumbersome ITT [3,4]. ere are some limitations to the 250 μg ACTH stimulation test, particularly that it is less reliable in the rst two months postpituitary surgery [18]; however, in our population, none of the ACTH stimulation tests was done within twelve weeks of pituitary surgery. Of note, Watts and Tindall also used the standard dose ACTH stimulation test 5-7 days and 1 month a er pituitary surgery [8], which may explain why their reported values are closer to ours.…”

Kickboxing sport as a new cause of traumatic brain injury‐mediated hypopituitarism

“…A peak cortisol level lower than 20 µ g/dl was accepted as ACTH deficiency. 18,19 Analytic methods of hormonal parameters Serum GH levels were measured by using immunoradiometric assay (IRMA) with commercial kit (DSL, Webster, TX, USA) intra-assay and interassay coefficients of variation (CV) were 3·1% and 5·9%, respectively. The minimum detection limit was 0·01 µ g/l, and GH standards were calibrated according to the World Health Organization reference standard 88/624.…”