Definition
A blood test to measure ACTH, a hormone secreted from the anterior pituitary.

Alternative Names
Serum adrenocorticotropic hormone; Adrenocorticotrophic hormone; Highly-sensitive ACTH

How the test is performed
Adult or child:

Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill with blood). A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

Infant or young child:

The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

The levels of ACTH vary with the body's circadian rhythms (the pattern of physiologic changes that occurs on a 24-hour cycle). This test is most accurate if it is performed early in the morning.

How to prepare for the test
The health care provider may advise the person to:

discontinue the use of steroid drugs
be at the laboratory or office where the blood is being drawn by or before 8 a.m., or when instructed
Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:

infant test or procedure preparation (birth to 1 year)
toddler test or procedure preparation (1 to 3 years)
preschooler test or procedure preparation (3 to 6 years)
schoolage test or procedure preparation (6 to 12 years)
adolescent test or procedure preparation (12 to 18 years)

How the test will feel
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

What the risks are

excessive bleeding
fainting or feeling lightheaded
hematoma (blood accumulating under the skin)
infection (a slight risk any time the skin is broken)
multiple punctures to locate veins

Why the test is performed
This test can help indicate the causes of hormone irregularities.

ACTH is a protein hormone secreted from the anterior pituitary gland. The main function of ACTH is the regulation of the steroid hormone cortisol, which is secreted by the adrenal cortex.