Clinical tests of the hypothalamo-pituitary-adrenocortical axis in cases of suspected adrenocortical insufficiency are based almost exclusively on the stimulation of pituitary ACTH release or adrenocortical release of ACTH-dependent steroids. The most widely applied tests of the hypothalamo-pituitary-adrenal axis in clinical practice are the short ACTH injection test (SAT), the insulin hypoglycemia test (IHT), the short metyrapone test (SMT) and the corticotropin-releasing hormone (CRH) test (1). In this review, the reliability of these tests in special clinical settings will be discussed under the aspect of dose—response relationships between plasma ACTH and cortisol in normal man.
Problems with the conventional SAT
If a patient is suspected to suffer from primary adrenal insufficiency (Addison's disease), the test for excluding or strengthening the suspicion is the SAT, comprising the injection (im or iv) of 250 μg of ACTH (1–24) (Synacthen®, Cosyntropin® or Cortrosyn®) and the measurement of plasma or serum cortisol 30 or