Low-Dose Adrenocorticotropin Test Reveals Impaired Adrenal Function in Patients Taking Inhaled Corticosteroids

The aim of the present study was to examine the use of low-dose ACTH-(l-24) stimulation for assessment of adrenal function and the detection of mild adrenal insufficiency. The criteria for normal response to ACTH-(l-24) are a peak cortisol level of more than 500 nmol/L (18.1 pg/dL) and an increment of the cortisol level above the basal one of more than 200 nmol/L (7.2 pg/dL). These criteria were satisfied by 32 of 33 healthy children and adults subjected to an ACTH-(l-24) dose 500 times lower (0.5 pg/1.73 m2) than the dose of 250 pg in the standard test. At 20 min, the peak cortisol level was the same in the low-dose test [(621 t 28 nmol/LJ (22.5 2 1.0 pg/dL)l as in the standard ACTH test [(654 + 31 nmol/L) (23.7 ? 1.1 pg/dL)]. Of 46 asthmatic patients who had been treated with inhaled beclomethasone dipropionate (482 5 42 wg/rn’ daily; n = 32) or budesonide (507 i 62 pg/rn’ daily; n = 14) for over 6 months, 16 (35%) failed to reach a cortisol peak of more than 500 nmol/L (18.1 pg/dL) following stimulation with 0.5 Fg ACTH-(l-24)/1.73 m2. Of these, 11(24%) showed a cortisol increment of less than 200 nmol/L (7.2 Fg/dL). These 16 patients, showing insufficient response to low-dose ACTH-(l-241, also had a significantly lower (P < 0.01) mean 24-h urinary free cortisol excretion [(71 ? 10 nmol/m2.24 h) (25.7 t 3.6 pg/rn2. 24 h)] than patients who responded normally [cl18 2 11 nmol/m2 .24 h) (42.8 + 4.0 pg/rn’ .24 h). Nonetheless, all but one of the poor responders to a 0.5 Fg ACTH showed normal stimulation with the standard 250 pg ACTH test. Therefore, it appears that a low-dose ACTH test is capable of revealing mild adrenal insufficiency, which is not detected by the standard high-dose ACTH test. (J Clin Endocrinol Metab 80: 12431246, 1995)