THE NEW HIGHLY SENSITIVE ADRENOCORTICOTROPIN ASSAY IMPROVES DETECTIONOF PATIENTS WITH PARTIAL ADRENOCORTICOTROPIN DEFICIENCY IN A SHORT-TERM METYRAPONE TEST

This study was designed to evaluate a short term metyrapone test using a highly sensitive (HS) IRMA ACTH assay and to evaluate the usefulnes s of a morning ACTH level as a screening test for partial ACTH deficie ncy. ACTH, 11-deoxycortisol and cortisol levels were evaluated over fo ur hours in the morning after a single 40 mg/kg oral dose of metyrapon e was administered at 0800 hours. 26 control children and 32 possibly pituitary deficient patients were evaluated. Based on 11-deoxycortisol levels alone, 17 of the patients passed the test, 11 patients failed the test and the result was inconclusive in four patients (12.5%). Eva luation of the increase in ACTH levels (Delta ACTH) following metyrapo ne identified three of the above four with partial ACTH deficiency. Th e Delta ACTH was consistent with the 11-deoxycortisol results in the r emainder of patients. There was no difference in morning ACTH levels b etween controls and patients with partial ACTH deficiency. The measure ment of ACTH using the HS IRMA assay, increases the sensitivity of the metyrapone test in detecting patients with partial ACTH deficiency. T his test may be used safely in pediatric patients on a repetitive basi s, especially in those children who may have progressive ACTH failure following hypothalamic-pituitary irradiation.