Adrenocorticotropic Hormone

Category: All Lab Tests

Adrenocorticotropic Hormone (ACTH)

Description

ACTH is created in the pituitary gland in response to another hormone, corticotropin-releasing hormone (CRH), by the hypothalamus. When this occurs adrenal glands make a hormone called cortisol, which helps the body manage stress. Cortisol is important for life, and its levels in the blood are closely controlled. When cortisol levels rise, ACTH levels fall. When cortisol levels fall, ACTH levels normally rise.
ACTH level is normally highest in the early morning and lowest in the evening. Also ACTH is released in bursts, and consequently its levels in the blood can vary from minute to minute.
Its concentration is measured by means of analysis of a blood sample drawn from the vein in the arm.

Purpose of the test

This test measures the level of adrenocorticotropic hormone (ACTH) in the blood to check for problems with the pituitary gland or the adrenal glands.
A test to measure ACTH is done to check for:
A problem with the adrenal glands or pituitary gland. A high level of ACTH and a low level of cortisol (or low ACTH and high cortisol levels) could be caused by a problem with the adrenal glands. Low levels of ACTH and cortisol could be caused by a problem with the pituitary gland.
Overproduction of ACTH. This may be caused by an overactive pituitary gland. In response, the adrenal glands release too much cortisol (one form of Cushing's syndrome).

Reference range values
6 a.m. to 8 a.m. < 80 pg/mL (< 18 pmol/L)
6 p.m. to 11 p.m. < 50 pg/mL ( < 11 pmol/L)

Abnormal findings

High levels of ACTH may be caused by:
- Emotional or physical stress.
- Addison's disease, Cushing's disease, or a tumor in the adrenal glands or the pituitary gland.
Low levels of ACTH may be caused by:
- Damage to the pituitary gland.
- An increased amount of cortisol from a tumor in the adrenal glands (Cushing's syndrome).