Adrenocorticotropic Hormone Stimulation Test

The hypothalamus secretes corticotropin-releasing hormone. This hormone stimulates the secretion of adrenocorticotropic hormone (ACTH) by the anterior pituitary gland. ACTH, in turn, causes the adrenal cortex to release the glucocorticoid hormone cortisol. Problems occurring in the adrenal cortex are considered “primary” disorders, whereas those occurring in the anterior pituitary gland are known as “secondary” disorders. It is important to determine whether a patient’s problem is of a primary or a secondary nature.
Various tests may be used to evaluate adrenal hypofunction through stimulation of the adrenal glands. The most common is the rapid ACTH test, for which cosyntropin (Cortrosyn) is administered. ACTH stimulation testing is especially valuable in the diagnosis of Addison’s disease. If plasma cortisol levels increase after administration of ACTH, the adrenal gland has the ability to function when stimulated and the cause of the adrenal insufficiency would be due to a problem in the pituitary gland. If, however, the plasma cortisol levels do not rise or increase only minimally, the problem lies with the adrenal gland. The test can also be used to check for recovery of the hypothalamus-pituitary-adrenal (HPA) axis during tapering of steroids after long-term use.