Adrenocorticotropic Hormone

ACTH (Adrenocorticotropic Hormone) Test

Test Overview

An adrenocorticotropic hormone test measures the level of adrenocorticotropic hormone (ACTH) in the blood. This test checks for problems with the pituitary gland or the adrenal glands. See an illustration of the pituitary gland or adrenal glands.

ACTH is made in the pituitary gland in response to the release of another hormone, called corticotropin-releasing hormone (CRH), by the hypothalamus. In turn, the adrenal glands then make a hormone called cortisol, which helps your body manage stress. Cortisol is needed for life, so its levels in the blood are closely controlled. When cortisol levels rise, ACTH levels normally fall. When cortisol levels fall, ACTH levels normally rise.

Both ACTH and cortisol levels change throughout the day. ACTH is normally highest in the early morning (between 6 a.m. and 8 a.m.) and lowest in the evening (between 6 p.m. and 11 p.m.). ACTH levels may be tested in the morning or evening if your doctor thinks that they are abnormal. Cortisol levels are often measured at the same time as ACTH.

Because ACTH is released in bursts, its levels in the blood can vary from minute to minute. Interpretation of the test results is difficult and often requires the skill of an endocrinologist.

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Author:	Sydney Youngerman-Cole, RN, BSN, RNC	Last Updated: August 3, 2006
Medical Review:	Caroline S. Rhoads, MD - Internal Medicine David C.W. Lau, MD, PhD, FRCPC - Endocrinology & Metabolism
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