Adrenocorticotropic Hormone (ACTH)

This test measures the level of adrenocorticotropic hormone (ACTH) in a sample of your blood. A hormone is a chemical messenger in your bloodstream that controls the actions of certain cells or organs. ACTH tells your adrenal glands, two small glands that sit above your kidneys, to make another hormone called cortisol.

Cortisol affects almost every organ and tissue in your body. It helps your body: Respond to stress (cortisol is sometimes called the 'stress hormone'); Reduce inflammation; Regulate blood glucose, also called blood sugar, and metabolism (how your body uses food for energy); Control blood pressure; Because ACTH controls how much cortisol you make, ACTH testing is usually done with a blood test to measure your cortisol levels. Normally, if cortisol levels drop too low, your ACTH levels will increase to trigger your adrenal glands to make more cortisol.

And if cortisol levels are high, ACTH levels will decrease so your adrenal glands will make less cortisol. Your ACTH and cortisol levels are controlled by a complex feedback system of hormones made in different parts of your body. These include your: Pituitary gland.

This small gland is in the base of your brain. It makes ACTH and other hormones.; Hypothalamus. This is a part of your brain.

It makes a hormone that tells your pituitary gland how much ACTH to make.; Adrenal glands. These glands respond to ACTH by making cortisol and releasing it into your bloodstream. The increased amount of cortisol in your blood signals your hypothalamus to stop making the hormone that tells your pituitary to make ACTH.; Conditions that affect any part of this system can affect the amount of cortisol in your body.

Too much or too little cortisol can lead to serious health problems.

Why this test is done

You may need this test if you had abnormal results on a cortisol test or have symptoms of too much or too little cortisol.

Symptoms of too much cortisol may vary. They may include:

• Weight gain
• Thin arms and legs
• Round face
• Increased fat around the base of the neck or between the shoulder blades
• Easy bruising
• Wide purple streaks on the stomach, breasts, hips, and under the arms
• Muscle weakness

Symptoms of too little cortisol include:

• Long-lasting fatigue
• Muscle weakness
• Loss of appetite
• Weight loss
• Abdominal (belly) pain

You may also need this test if you have symptoms of hypopituitarism. Symptoms will vary depending on which pituitary hormones are affected and how low the levels are. If ACTH is decreased, you may have symptoms from low cortisol levels.

If a tumor is causing hypopituitarism, symptoms may also include headaches and vision problems.

How to prepare

Your health care provider will tell you how to prepare for your test. You may need to fast (not eat or drink) for several hours before your test. Blood samples for ACTH testing are often taken early in the morning when ACTH levels are at their highest for the day.

You may need to stop taking certain medicines before this test, so tell your provider about everything you take. But don't stop taking any medicines unless your provider tells you to.

Sample type

Blood

Other names for this test

Adrenocorticotropic hormone blood test, corticotropin