Why am I having this test?

The adrenocorticotropic hormone, also called ACTH, is produced by the pituitary gland, a tiny organ in the base of the brain. ACTH is involved in a process that produces other hormones, such as cortisol. Cortisol is made by the adrenal glands, which are two small glands located above the kidneys.

Your health care provider may order the ACTH test to help diagnose conditions in which cortisol levels are abnormal, such as Cushing’s syndrome or Addison’s disease.

What is being tested?

The ACTH test measures the level of ACTH in your blood. The levels of ACTH vary with the time of day and are highest in the morning. These changes during the day are called diurnal variation.

What kind of sample is taken?

A blood sample is required for this test. It is usually collected by inserting a needle into a blood vessel.

How do I prepare for this test?

• Do not eat or drink anything after midnight on the night before the test or as directed by your health care provider.

• You may have this test both in the morning and in the evening. This checks for diurnal variation.

How are the results reported?

Your test results will be reported as a value. Your health care provider will compare your results to normal ranges that were established after testing a large group of people (reference ranges). Reference ranges may vary among labs and hospitals. For this test, common reference ranges are:

What do the results mean?

• Increased levels of ACTH may mean that you have:

  • Addison’s disease (primary adrenal insufficiency). This results from direct damage to the adrenal glands. The damaged glands produce little cortisol, which forces the pituitary gland to make more ACTH in an attempt to raise the level of cortisol in the body.

  • Congenital adrenal hyperplasia. With this condition, the adrenal glands do not make enough cortisol for the body’s needs. Low levels of cortisol in the body signal the pituitary gland to release more ACTH in an attempt to stimulate cortisol production.

  • Cushing’s disease. This is caused by a pituitary gland tumor. The tumor may secrete excess ACTH. Excess ACTH overstimulates the adrenal glands, leading to an increase in cortisol.

  • Stress.

• Decreased levels of ACTH may mean that you have:

  • Secondary adrenal insufficiency. This is due to decreased activity of the adrenal glands as a result of decreased ACTH release from the pituitary gland.

  • Decreased activity of the pituitary gland (hypopituitarism).

  • An adrenal tumor (adenoma or carcinoma).

  • Cushing’s syndrome. This is a condition of excess cortisol in the body. It is caused by medicines, enlarged adrenal glands, and tumors of the pituitary gland. Excess cortisol in the body signals the pituitary gland to decrease the amount of ACTH it produces.

  • Steroid use.

Talk with your health care provider about what your results mean.

Questions to ask your health care provider

Summary

• The adrenocorticotropic hormone, also called ACTH, is involved in a process that produces other hormones, such as cortisol.

• Your health care provider may order the ACTH test to help diagnose conditions in which cortisol levels are abnormal, such as Cushing’s syndrome or Addison’s disease.

• Do not eat or drink anything after midnight on the night before the test or as directed by your health care provider.

• You may have this test both in the morning and in the evening. This checks for diurnal variation.

This information is not intended to replace advice given to you by your health care provider. Make sure you discuss any questions you have with your health care provider.