What is an adrenocorticotropic hormone (ACTH) test?

This test measures the level of adrenocorticotropic hormone (ACTH) in the blood. ACTH is a hormone made by the pituitary gland, a small gland at the base of the brain. ACTH controls the production of another hormone called cortisol. Cortisol is made by the adrenal glands, two small glands located above the kidneys. Cortisol plays an important role in helping you to:

• Respond to stress
• Fight infection
• Regulate blood sugar
• Maintain blood pressure
• Regulate metabolism, the process of how your body uses food and energy

Too much or too little cortisol can cause serious health problems.

Other names: Adrenocorticotropic hormone blood test, corticotropin

What is it used for?

An ACTH test is often done along with a cortisol test to diagnose disorders of the pituitary or adrenal glands. These include:

• Cushing's syndrome, a disorder in which the adrenal gland makes too much cortisol. It may be caused by a tumor in the pituitary gland or the use of steroid medicines. Steroids are used to treat inflammation but can have side effects that affect cortisol levels.
• Cushing's disease, a form of Cushing's syndrome. Cushing's disease is usually caused by a noncancerous tumor of the pituitary gland. The tumor makes too much ACTH. This causes the adrenal glands to make too much cortisol.
• Addison disease, a condition in which the adrenal gland doesn't make enough cortisol.
• Hypopituitarism, a disorder in which the pituitary gland does not make enough of some or all of its hormones.

Why do I need an ACTH test?

You may need this test if you have symptoms of too much or too little cortisol.

Symptoms of too much cortisol include:

• Weight gain
• Buildup of fat in the shoulders
• Pink or purple stretch marks (lines) on the abdomen, thighs, and/or breasts
• Skin that bruises easily
• Increased body hair
• Muscle weakness
• Fatigue
• Acne

Symptoms of too little cortisol include:

• Weight loss
• Nausea and vomiting
• Diarrhea
• Abdominal pain
• Dizziness
• Darkening of the skin
• Salt craving
• Fatigue

You may also need this test if you have symptoms of hypopituitarism. Symptoms will vary depending on the severity of the disease, but may include the following:

• Loss of appetite
• Irregular menstrual periods and infertility in women
• Loss of body and facial hair in men
• Lower sex drive in men and women
• Sensitivity to cold
• Urinating more often than usual
• Fatigue

What happens during an ACTH test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for the test?

You may need to fast (not eat or drink) overnight before testing. Tests are usually done early in the morning because cortisol levels change throughout the day.

Are there any risks to the test?

There is very little risk to having a blood test. You may have slight pain or bruise at the spot where the needle was put in, but most symptoms go away quickly.