A baseline ACTH level measured on the same blood sample as your cortisol level can assess your cortisol production. An ACTH stimulation test measures the ability of your adrenal glands to respond to stress.

ACTH (adrenocorticotropic hormone) is a hormone produced in the front part of the pituitary gland in the brain. It regulates levels of the steroid hormone cortisol, which is released from the adrenal gland.

ACTH is also known as:

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

An ACTH test may refer to a baseline test of your ACTH levels. If there is an issue with your pituitary gland, it may produce too much or too little ACTH. This can also affect your body’s production of cortisol and adrenaline.

An ACTH test may also refer to an ACTH stimulation test, also known as a cosyntropin stimulation test. This test helps doctors detect diseases associated with too little cortisol in the body.

Possible causes can include:

Doctors typically perform a baseline ACTH test followed by an ACTH stimulation test, which tests your cortisol levels in response to stress.

A baseline test of your cortisol and ACTH levels is usually done first thing in the morning. A healthcare professional may schedule your test for very early in the morning.

Then, you typically receive an intramuscular (injected into a muscle) dose of cosyntropin. Cosyntropin is a synthetic form of ACTH that typically stimulates the production of cortisol.

About 30 and/or 60 minutes after the injection, a healthcare professional will test your cortisol levels by taking a blood sample. They may take a blood sample by drawing blood from a vein, usually inside the elbow.

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

A doctor may order this test if they suspect pituitary or adrenal gland dysfunction, including if you have symptoms of high or low cortisol. These symptoms can vary widely from person to person. They can be a sign of additional health problems.

Symptoms of high cortisol can include:

The symptoms of low cortisol can include:

Typical baseline ACTH values range from 10 to 60 picograms per milliliter (pg/mL). These value ranges may vary slightly depending on the laboratory. A level outside of this range may be an indicator of certain health conditions.

During an ACTH stimulation test, doctors measure your cortisol levels in response to stress. If your cortisol levels do not rise or rise insufficiently after the cosyntropin injection compared to your baseline levels, you may have adrenal insufficiency.

Depending on the result, a doctor may need to order additional tests to make a diagnosis.

Possible diagnoses can include:

  • Addison disease: Addison’s disease occurs when the adrenal cortex is damaged and the adrenal glands cannot produce enough of the hormones cortisol and aldosterone.
  • Hypopituitarism: Hypopituitarism occurs when the pituitary gland does not make enough of some or all of its hormones.
  • Congenital adrenal hyperplasia: If you have congenital adrenal hyperplasia, it means that due to a birth defect, your adrenal glands cannot produce cortisol and aldosterone at typical rates.
  • Adrenoleukodystrophy: Adrenoleukodystrophy refers to multiple rare conditions, including Addison’s disease, that affect the nervous system and adrenal glands.
  • Nelson’s syndrome: This rare condition occurs if you have an ACTH-producing tumor in the pituitary gland after the surgical removal of both adrenal glands due to Cushing’s disease.

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

Having your blood drawn may cause bleeding or bruising at the injection site. 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 stimulation test are rare.

Diagnosis of a condition that affects your ACTH or cortisol production can be highly complex. A doctor may need to order additional laboratory tests and perform a physical examination before making a diagnosis.

If an ACTH-secreting tumor causes of excessive cortisol production, you can talk with a doctor about medical treatment and surgery. Doctors usually recommend surgery for ACTH-secreting tumors and other tumors that cause a high ACTH level. Sometimes, they may recommend medication to bring your cortisol levels to a typical range. It can be less effective than surgery but doctors may recommend it in certain cases, including if you are not well enough for surgery.

Hypercortisolism due to adrenal tumors typically requires surgery.

A high ACTH level may also indicate a condition that causes insufficient cortisol production, such as Addison’s disease. If you have a condition such as Addison’s disease that affects hormone production, a doctor typically prescribes medications to replace the hormones your body is not producing. You may also need medications to reduce inflammation.

The following includes frequently asked questions about ACTH levels and the ACTH stimulation test.

What does an ACTH stimulation test evaluate?

An ACTH stimulation test evaluates the adrenal gland’s ability to respond to stress. It may be one of multiple tests that help doctors diagnose disorders or tumors of the pituitary or adrenal glands.

How do I prepare for an ACTH stimulation test?

A doctor typically requests a list of all medications, supplements, and other drugs you may be using, as they may affect your results. You may need to stop taking certain medications, including steroids, before an ACTH stimulation test.

An ACTH baseline test measures your baseline levels of adrenocorticotropic hormone.

An ACTH stimulation test measures the adrenal gland’s ability to respond to stress.

These two tests together can help doctors diagnose health conditions that affect your pituitary or adrenal gland function.

You may need additional tests to reach a complete diagnosis.