The Test Sample
What is being tested?
Adrenocorticotropic hormone (ACTH) is a hormone that stimulates the production of cortisol. Cortisol is a steroid hormone important for regulating glucose, protein, and lipid metabolism, suppressing the immune system's response, and helping to maintain blood pressure. This test measures the amount of ACTH in the blood.
ACTH is produced by the pituitary gland. Located below the brain in the center of the head, the pituitary gland is part of the endocrine system, a network of glands that work together to produce hormones that act on organs, tissues, and other glands to regulate systems throughout the body.
Normally, ACTH levels increase when cortisol is low and fall when cortisol is high. When cortisol levels fall in the blood, the hypothalamus produces corticotropin-releasing hormone (CRH). This stimulates the production of ACTH by the pituitary, which in turn stimulates the production of cortisol by the adrenal glands, small organs located at the top of each kidney. In order for appropriate amounts of cortisol to be made, the hypothalamus and both the pituitary and adrenal glands must be functioning properly.
Conditions that affect the pituitary or adrenal glands can increase or decrease the amount of ACTH and cortisol the glands produce and interfere with their regulation. This can cause signs and symptoms associated with an excess or deficiency of cortisol. Some tumors found outside of the pituitary in locations such as the lungs can also increase cortisol concentrations by producing ACTH.
How is the sample collected for testing?
A blood sample is taken by needle from a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
Your doctor may request that you fast overnight before testing. Blood is typically drawn in the morning, about 8 a.m.