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:

  • an adrenal or pituitary malfunction
  • a pituitary tumor
  • an adrenal tumor
  • a lung tumor


How the ACTH Test Is Performed

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 probably 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.


Why the ACTH Test Is Performed

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:

  • obesity
  • a rounded face
  • fragile, thin skin
  • purple lines on the abdomen
  • weak muscles
  • acne
  • an increased amount of body hair
  • high blood pressure
  • low potassium levels
  • high bicarbonate level
  • high glucose levels
  • diabetes

The symptoms of low cortisol include:

  • weak muscles
  • fatigue
  • weight loss
  • increased skin pigmentation in areas not exposed to the sun
  • a loss of appetite
  • low blood pressure
  • low blood glucose levels
  • low sodium levels
  • high potassium levels
  • high calcium levels


What ACTH Test Results Can Mean

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:

  • Addison’s disease
  • adrenal hyperplasia
  • Cushing’s disease
  • an ectopic tumor that produces ACTH
  • adrenoleukodystrophy, which is very rare
  • Nelson’s syndrome, which is very rare

A low level of ACTH may be a sign of:

  • adrenal tumor
  • exogenous Cushing’s syndrome
  • hypopituitarism

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



Risks of an ACTH Test

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


What to Expect After an ACTH Test

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

Certain drugs increase or decrease the level of cortisol and ACTH in the blood. These drugs can be used to find the cause of any underlying condition and help your doctor find the best treatment for you. Treatment usually involves prescription medications or even surgery in the case of certain tumors.

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