What is an ACTH test?

Adrenocorticotropic hormone (ACTH) is a hormone produced in the anterior, or front, pituitary gland in the brain. The function of ACTH is to regulate levels of the steroid hormone cortisol, which released from the adrenal gland.

ACTH is also known as:

  • adrenocorticotropic hormone
  • serum adrenocorticotropic hormone
  • highly-sensitive ACTH
  • corticotropin
  • cosyntropin, which is a drug form of ACTH

An ACTH test measures the levels of both ACTH and cortisol in the blood and helps your doctor detect diseases that are associated with too much or too little cortisol in the body. Possible causes of these diseases include:

Your doctor may advise you not to take any steroid drugs before your test. These can affect the accuracy of the results.

The test is usually done first thing in the morning. ACTH levels are highest when you’ve just woken up. Your doctor will likely schedule your test for very early in the morning.

ACTH levels are tested using a blood sample. A blood sample is taken by drawing blood from a vein, usually from the inside of the elbow. Giving a blood sample involves the following steps:

  1. A healthcare provider first cleans the site with an antiseptic to kill germs.
  2. Then, they’ll wrap an elastic band around your arm. This causes the vein to swell with blood.
  3. They’ll gently insert a needle syringe into your vein and collect your blood in the syringe tube.
  4. When the tube is full, the needle is removed. The elastic band is then removed, and the puncture site is covered with sterile gauze to stop the bleeding.

Your doctor may order an ACTH blood test if you have symptoms of too much or too little cortisol. These symptoms can vary widely from person to person and are often a sign of additional health problems.

If you have a high cortisol level, you may have:

The symptoms of low cortisol include:

Normal values of ACTH are 9 to 52 picograms per milliliter. Normal value ranges may vary slightly depending on the laboratory. Your doctor will explain your test results to you.

A high level of ACTH may be a sign of:

A low level of ACTH may be a sign of:

Taking steroid medications can cause low levels of ACTH, so be sure to tell your doctor if you are on any steroids.

Blood tests are normally well-tolerated. Some people have smaller or larger veins, which may make taking a blood sample more difficult. However, risks associated with blood tests like the ACTH hormone test are rare.

Uncommon risks of having blood drawn include:

  • excessive bleeding
  • lightheadedness or fainting
  • hematoma, or blood pooling under the skin
  • infection at the site

Diagnosing ACTH diseases can be highly complex. Your doctor may need to order more laboratory tests and perform a physical examination before they can make a diagnosis.

For ACTH secreting tumors, surgery is usually indicated. Sometimes, drugs such as cabergoline can be used to normalize cortisol levels. Hypercortisolism due to adrenal tumors usually requires surgery as well.