ACTH (Cosyntropin) Stimulation Test

Written by Gretchen Holm
Medically Reviewed by Brenda B. Spriggs, MD, MPH, FACP

ACTH Stimulation Test

Your pituitary gland, a pea-sized gland located at the base of your brain, produces many types of hormones, including the adrenocorticotropic hormone (ACTH). ACTH stimulates the adrenal glands, which sit atop the kidneys, to release two hormones, cortisol and adrenaline, also known as epinephrine. These hormones help you respond to stress in a healthy way and support your immune system. Cortisol is a steroid hormone that affects many different systems in the body such as:

  • Circulatory system
  • Immune system
  • Nervous system
  • Bone metabolism
  • Metabolism of nutrients such as carbohydrates, fats and protein

Adrenaline or epinephrine is a hormone responsible for maintaining normal nervous system and circulatory function. When there is a stressful situation, this hormone along with another hormone, norepinephrine, is responsible for the protective fight-or-flight response.

If a doctor suspects that your adrenal glands might not be functioning properly, he or she may perform an ACTH (cosyntropin) stimulation test. This test will require you to receive an injection of cosyntropin, a synthetic portion of ACTH and to have two blood samples drawn, one before the injection and one after the injection. These samples will measure the level of cortisol in your blood.

This ACTH stimulation test measures how your adrenal glands react to the ACTH in your blood by measuring your body’s cortisol levels. It’s important not to confuse this test with an ACTH test, which simply measures the ACTH levels in your blood.

Why You Might Need an ACTH (Cosyntropin) Stimulation Test

Your doctor may order an ACTH (cosyntropin) stimulation test if he or she thinks that your adrenal glands are not functioning properly. It is used to diagnose adrenal insufficiency known as Addison’s disease. It is also used to determine if the pituitary gland is not working properly- hypopituitarism. This could be a cause of secondary adrenal insufficiency. The ACTH test along with the ACTH blood level is also used to diagnose excessive cortisol secretion from the adrenal gland such as in cases of Cushing’s.

Below are some of the signs and symptoms that may alert your doctor to order an ACTH stimulation test. They are fairly non-specific but if they are progressive and interfere with your daily activities and normal functioning, they should be evaluated:

  • unexplained weight loss
  • low blood pressure
  • loss of appetite
  • muscle weakness
  • muscle and joint pain
  • fatigue
  • darkening discoloration of the skin
  • mood changes
  • depression
  • irritability

In cases of excess secretion of cortisol, some characteristic signs and symptoms include:

If you experience these symptoms, your doctor might order an ACTH (cosyntropin) stimulation test. This can help him or her decide if malfunctioning adrenal glands are the cause of your symptoms.

Preparation for an ACTH (Cosyntropin) Stimulation Test

Preparation for this test can vary, so make sure to get clear instructions from your doctor. You will likely need to fast for eight hours before the test. Your doctor might advise you to stop taking certain medications for 24 hours prior to testing. Some common medications that can affect cortisol levels include but are not limited to:

  • steroid medications
  • male hormones
  • birth control pills
  • estrogen
  • amphetamines
  • lithium
  • dilantin (anti-seizure drug)

For this reason, it’s important to make sure your doctor knows about all the medications you’re taking, even over-the-counter drugs.

How Is an ACTH (Cosyntropin) Stimulation Test Performed?

A healthcare provider will take a blood sample when you arrive for your procedure. This blood sample will measure your blood cortisol levels. Your doctor can use this sample as a baseline against which to compare the results of the second blood test.

Next, you will receive an injection of cosyntropin, a synthetic portion of ACTH. This hormone should trigger the adrenal glands to produce cortisol. You will then wait for about an hour while your body reacts to the cosyntropin injection.

After this hour is up, your healthcare provider will take a second blood sample. This sample will reflect your cortisol levels after your body has had time to react to the injection.

Both of your blood samples will be tested for their cortisol levels. You will typically get the results of your ACTH stimulation test in one to two weeks.

What Do ACTH (Cosyntropin) Stimulation Test Results Mean?

Your blood cortisol levels after the ATCH stimulation should be greater than 18 to 20 micrograms per deciliter (mcg/dL), according to the National Institutes of Health (NIH). However, normal results may vary slightly, so talk to your doctor if you are concerned.

Blood cortisol levels below the acceptable range following stimulation are considered low. These abnormal results on the ATCH stimulation test may mean that you have an adrenal condition such as acute adrenal crisis, Addison’s disease, hypopituitarism, or pituitary tumors. Blood cortisol levels above the expected range following ACTH stimulation maybe consistent with Cushing’s and further testing will be required to confirm this diagnosis. All causes of abnormal result must be ruled out and because this testing can be complicated, you should talk to your doctor about how to proceed.

What Are the Risks of an ACTH (Cosyntropin) Stimulation Test

Slight risks are present any time you have blood drawn. These include:

  • light-headedness
  • infection
  • excessive bleeding
  • fainting
  • hematoma
  • inflammation of the vein at the site of entry of the blood drawing

You will probably feel mild to moderate pain when the needle is inserted. You might also feel throbbing in the puncture site after the needle has been removed, there may be mild bleeding following withdrawal of the needle, and you could develop a small bruise in the area. All of these symptoms are self-limited and do not cause any serious lasting effects.

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