Adrenocorticotropic Hormone (ACTH) Test

About the Test

Purpose of the test

ACTH blood tests are used, usually in conjunction with cortisol tests, to help detect, diagnose, and monitor conditions associated with excessive or deficient cortisol in the body. These conditions include:

• Cushing’s disease: excess cortisol due to an ACTH-producing tumor in the pituitary gland (usually a benign tumor)
• Cushing’s syndrome: the symptoms and signs associated with excess cortisol; in addition to Cushing’s disease, Cushing’s syndrome may be due to an adrenal tumor, adrenal hyperplasia, the use of steroid medications, or an ACTH-producing tumor located outside the pituitary (ectopic), such as in the lungs.
• Addison’s disease (primary adrenal insufficiency): decreased cortisol production due to adrenal gland damage
• Secondary adrenal insufficiency: decreased cortisol production because of pituitary dysfunction
• Hypopituitarism: pituitary dysfunction or damage that leads to decreased (or no) hormone production by the pituitary, including ACTH production

Measuring both ACTH and cortisol can help to differentiate among some of these conditions because the level of ACTH normally changes in the opposite direction to the level of cortisol.

If abnormal levels are detected, a health care practitioner will do additional testing to help confirm the findings and help determine the cause.

What does the test measure?

ACTH is produced by the pituitary gland. Located below the brain in the center of the head, the pituitary gland is part of the endocrine system, a network of glands that work together to produce hormones that act on organs, tissues, and other glands to regulate systems throughout the body.

Normally, ACTH levels increase when cortisol is low and fall when it is high. In response to a drop in the blood cortisol level, the hypothalamus produces corticotropin-releasing hormone (CRH). This stimulates the production of ACTH by the pituitary, which in turn stimulates the production of cortisol by the adrenal glands, small organs located at the top of each kidney.

The hypothalamus, pituitary, and adrenal glands must function properly to make the appropriate amounts of cortisol.

Conditions that affect the hypothalamus, pituitary, or adrenal glands can interfere with regulating ACTH and cortisol production, increasing or decreasing how much of the hormones the glands produce. This can cause signs and symptoms associated with an excess or deficiency of cortisol.

Conditions that affect ACTH include Cushing’s disease, adrenal insufficiency (Addison’s disease), and hypopituitarism. Some tumors found outside of the pituitary in locations such as the lungs can also increase cortisol concentrations by producing ACTH.

When should I get this test?

An ACTH test may be ordered after a cortisol test reveals abnormal results and when someone has signs or symptoms associated with excess or deficient cortisol.

Too much cortisol can cause symptoms that include:

• Obesity, with majority of the weight on the trunk of the body and not the arms and legs
• Fat collection between the shoulders
• Rounded, red face
• Fragile and thin skin
• Purple lines on the abdomen
• Muscle weakness
• Acne
• Skin infections
• Increased body hair
• Fatigue

These are often accompanied by findings such as high blood pressure, low potassium, high bicarbonate, high glucose levels, and sometimes diabetes.

If you have insufficient cortisol production you may exhibit symptoms such as:

• Muscle weakness
• Fatigue
• Weight loss
• Increased skin pigmentation, even in areas not exposed to the sun
• Loss of appetite
• Diarrhea, nausea and vomiting
• Dizziness
• Salt cravings

These are often accompanied by findings such as low blood pressure, low blood glucose, low sodium, high potassium, and high calcium.

Symptoms suggestive of hypopituitarism typically include several of the following:

• Loss of appetite
• Fatigue
• Irregular menstrual cycle
• Dysfunction of sex organs (hypogonadism)
• Decreased sex drive
• Frequent nighttime urination
• Unexplained weight loss
• Hot flashes
• Cold sensitivity

When the condition is due to a pituitary tumor (usually benign), the affected person may also have symptoms associated with the compression of nearby cells and nerves. For example, the tumor can cause a change in a pattern of headaches. It can also affect the nerves controlling vision, causing symptoms such as “tunnel vision” (inability to see things off to the side), loss of vision to some localized areas, or double vision.