Adrenocorticotropic Hormone (ACTH): Testing and Levels

What Is ACTH?

ACTH, or adrenocorticotropic hormone, is a hormone made by the pituitary gland. This small gland sits at the base of your brain and plays a big role in regulating your body.

ACTH signals the adrenal glands, located above the kidneys, to release cortisol into the bloodstream. Cortisol helps your body respond to stress, maintain blood pressure, regulate metabolism, and control inflammation.

Doctors often measure ACTH levels when checking how well your pituitary and adrenal glands are working. This test helps diagnose conditions like adrenal insufficiency, Cushing’s syndrome, or pituitary disorders.

When Is ACTH Testing Recommended?

ACTH testing checks if your body is producing the right amount of this hormone and cortisol. Doctors may recommend the test if they suspect problems with the adrenal or pituitary glands.

You may need an ACTH test if you have:

• Unexplained weight loss or gain, to check if hormone imbalance is causing it.
• Weakness, fatigue, or low energy, to see if your adrenal glands are underactive.
• High blood pressure that is hard to control, which can sometimes point to cortisol problems.
• Skin darkening (hyperpigmentation), which may signal high ACTH.
• Symptoms of Cushing’s syndrome include fat deposits in the upper back, round face, or stretch marks.
• Unexplained low blood sugar, which can also be hormone-related.

How Is ACTH Testing Conducted?

ACTH is measured with a blood test. A healthcare provider draws blood from a vein, usually in the morning when ACTH and cortisol levels are highest.

ACTH testing is sometimes included as part of a broader hormonal panel. This panel measures several hormones at once to give doctors a clearer picture of how your glands are functioning.

This test is often ordered as part of a hormonal evaluation and may be done alongside a cortisol test. In some cases, your doctor may order an ACTH stimulation test. This involves giving an injection that stimulates your adrenal glands to see how they respond.

Test Preparation

• Schedule the test for the morning if possible, since hormone levels change throughout the day.
• Avoid eating or drinking anything except water for several hours before the test if your doctor advises fasting.
• Tell your provider about any medications or supplements you are taking, as some can affect results.
• Try to stay relaxed before and during the test because stress can influence hormone levels.

What Are the Normal ACTH Levels?

Normal ACTH levels in the blood usually range from about 1-60 pg/ml (1.3-16.7 pmol/L)  when measured in the morning.

Note: The units of measurement and the normal ranges can differ depending on the laboratory and the specific methods used.

What Do Abnormal Levels Mean?

When your ACTH levels are outside the normal range, it may signal that your pituitary or adrenal glands are not working properly. Both high and low levels have specific causes and implications.

ACTH High Levels

High ACTH means your pituitary is releasing too much of the hormone or your adrenal glands are not responding properly.

Possible causes include:

• Addison’s disease: adrenal glands produce too little cortisol, so ACTH rises to compensate.
• Cushing’s disease: a pituitary tumor produces too much ACTH, raising cortisol.
• Ectopic ACTH production: some tumors elsewhere in the body (like lungs) produce ACTH.
• Congenital adrenal hyperplasia: a genetic condition that reduces cortisol production and increases ACTH.

• Consult an endocrinologist for a full evaluation and follow-up tests.
• Follow a balanced diet and manage stress levels while waiting for diagnosis.
• Keep track of your symptoms and report any changes to your doctor.
• Prepare for possible imaging tests, like MRI or CT scans, if your doctor suggests them.

ACTH Low Levels

Low ACTH means your pituitary gland isn’t producing enough hormone, or your adrenal glands are overactive and suppressing ACTH production.

Possible causes include:

• Pituitary gland problems, like tumors, injury, or infections affecting hormone production.
• Prolonged steroid use can suppress ACTH and cortisol levels.
• Adrenal tumors, which produce excess cortisol, lowering ACTH.
• Hypothalamic disorders which interfere with signals to the pituitary gland.

• See an endocrinologist to identify the underlying cause.
• Discuss whether any medications you take could be affecting your hormone levels.
• Consider further tests to check cortisol and other hormone levels.
• Follow up with regular monitoring as your doctor advises.

Which Specialist Should You Consult?

If your ACTH levels are abnormal, it’s best to see an endocrinologist. These doctors specialize in hormone-related conditions and can guide you through diagnosis, treatment, and ongoing care.

If your symptoms are severe, such as fainting, severe weakness, or confusion, seek emergency medical attention right away.