Adrenocorticotropic Hormone (ACTH)

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 tumour 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. In this disorder, the pituitary gland makes too much ACTH. It is usually caused by a non-cancerous tumour of the pituitary gland.
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
The 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

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 bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

Results of an ACTH test are often compared with the results of cortisol tests and may show one of the following:

High ACTH and high cortisol levels: This may mean Cushing’s disease.
Low ACTH and high cortisol levels: This may mean Cushing’s syndrome or a tumor of the adrenal gland.
High ACTH and low cortisol levels: This may mean Addison disease.
Low ACTH and low cortisol levels. This may mean hypopituitarism.

If you have questions about your results, talk to your health care provider.

Is there anything else I need to know about an ACTH test?

A test called an ACTH stimulation test is sometimes done instead of an ACTH test to diagnose Addison disease and hypopituitarism. An ACTH stimulation test is a blood test that measures cortisol levels before and after you’ve received an injection of ACTH.

References

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