Adrenocorticotropic Hormone

The adrenocorticotropic hormone (ACTH) test measures the amount of ACTH in your blood. This hormone, made by your pituitary gland, tells your adrenal glands to produce cortisol. The test helps your doctor check how well these glands are working together and can help diagnose conditions related to too much or too little cortisol.

What is Adrenocorticotropic Hormone?

Adrenocorticotropic hormone (ACTH) is a vital hormone produced by your pituitary gland, a small gland located at the base of your brain. Its main job is to signal your adrenal glands, which sit on top of your kidneys, to release cortisol, a crucial stress hormone.

Your pituitary gland acts like a control center, sending messages throughout your body. One of these messages is ACTH. When ACTH travels through your bloodstream to your adrenal glands, it stimulates them to make and release cortisol. Cortisol is often called the "stress hormone" because it helps your body respond to stress, but it also plays many other important roles. It helps regulate your metabolism, reduce inflammation, control blood sugar, and maintain blood pressure. The amount of ACTH your pituitary gland releases depends on the level of cortisol in your blood. If cortisol levels are low, the pituitary gland usually releases more ACTH to encourage the adrenal glands to make more. If cortisol levels are high, the pituitary gland typically releases less ACTH. This is a natural feedback loop that helps keep your body balanced and ensures your body has the right amount of cortisol.

Why it's ordered

Your doctor may order an ACTH test if you have symptoms suggesting your body is making too much or too little cortisol. This test helps pinpoint whether the problem lies with your pituitary gland, which produces ACTH, or your adrenal glands, which produce cortisol in response to ACTH.

Symptoms that might lead to an ACTH test include unexplained weight gain or loss, muscle weakness, fatigue, high blood pressure (hypertension), changes in skin color, or unusual hair growth. These symptoms can be signs of an imbalance in your body's cortisol levels. For example, if you have symptoms of high cortisol, such as a rounded face, a hump between your shoulders, or thin skin that bruises easily, your doctor might suspect Cushing's syndrome. An ACTH test can help determine if the high cortisol is due to a problem in your pituitary gland (Cushing's disease) or a problem directly in your adrenal glands. Conversely, if you have symptoms of low cortisol, such as extreme fatigue, weight loss, low blood pressure, or dark patches on your skin, your doctor might suspect Addison's disease (primary adrenal insufficiency) or secondary adrenal insufficiency. The ACTH test helps differentiate between these conditions by showing whether your pituitary gland is producing too much, too little, or a normal amount of ACTH in response to your body's cortisol needs.

How to prepare

Preparing for an ACTH test often requires specific instructions to ensure accurate results. You will usually need to have your blood drawn in the morning, as ACTH levels naturally change throughout the day. Your doctor may also ask you to fast and discuss any medications you are currently taking.

ACTH levels in your blood naturally fluctuate, typically being highest in the early morning and lowest in the evening. Because of this, your doctor will usually schedule your blood test between 7:00 AM and 10:00 AM to capture your peak levels. You may also be asked to fast for 8 to 12 hours before the test, meaning you should not eat or drink anything except water during that time. It is crucial to tell your doctor about all medications you are taking, including prescription drugs, over-the-counter medicines, and any herbal supplements. Certain medications, such as corticosteroids (steroids), estrogens, and amphetamines, can affect ACTH levels and might need to be temporarily stopped or adjusted before the test. However, never stop or change your medication without first talking to your doctor. They will provide specific guidance tailored to your health needs.

What to expect during

During an ACTH test, a healthcare professional will collect a small sample of your blood, typically from a vein in your arm. The procedure is quick and straightforward, similar to any routine blood test, and usually causes only a brief, mild sensation as the needle is inserted.

When you arrive for your test, a phlebotomist (a healthcare professional trained in drawing blood) will usually ask you to sit comfortably. They will clean a small area of skin, typically on the inside of your elbow, with an antiseptic wipe. To make the vein more visible and easier to access, they will tie an elastic band (tourniquet) around your upper arm. Once a suitable vein is found, a small needle will be gently inserted into the vein. You might feel a quick pinch or sting. The blood will then be collected into a small tube. After enough blood has been drawn, the tourniquet will be removed, and the needle will be withdrawn. A small bandage or cotton ball will be placed over the site to stop any minor bleeding. The entire process usually takes only a few minutes, and the blood sample is then sent to a laboratory for analysis.

Understanding your results

Your ACTH test results, when interpreted by your doctor alongside your cortisol levels and other tests, provide important information about the health of your pituitary and adrenal glands. These results help determine the specific cause of conditions involving abnormal cortisol production, guiding appropriate treatment.

Normal ACTH levels can vary slightly depending on the laboratory, but generally fall within a specific range. Your doctor will compare your results to these reference ranges. * **High ACTH and Low Cortisol:** This combination often points to primary adrenal insufficiency, also known as Addison's disease. In this case, your adrenal glands are not producing enough cortisol, and your pituitary gland is working harder, making more ACTH to try and stimulate them. * **High ACTH and High Cortisol:** This usually indicates Cushing's disease. Here, a tumor in your pituitary gland is producing too much ACTH, which then overstimulates your adrenal glands to make excessive cortisol. * **Low ACTH and Low Cortisol:** This pattern suggests secondary adrenal insufficiency. Your pituitary gland is not producing enough ACTH, leading to your adrenal glands making too little cortisol. * **Low ACTH and High Cortisol:** This often means there's a problem directly with your adrenal glands, such as a tumor, that is producing too much cortisol on its own. The high cortisol then signals your pituitary gland to reduce its ACTH production. It is crucial to remember that these are general interpretations. Your doctor will consider your symptoms, medical history, and the results of any other tests you have had to provide a complete and accurate diagnosis. Never attempt to interpret your own results or make medical decisions based solely on these general guidelines.

Risks

The risks associated with an ACTH blood test are minimal and are similar to those of any routine blood draw. Most people experience no complications, but minor issues like bruising or slight discomfort at the needle site can occur.

As with any blood test, there are a few minor risks, though serious complications are rare. You might experience some slight pain or a stinging sensation when the needle is inserted. After the blood draw, it's common to have a small bruise or tenderness at the site where the blood was taken. Applying gentle pressure to the area immediately after the test can help reduce bruising. Less commonly, some people might feel lightheaded or dizzy, or even faint, during or after the blood draw. Rarely, there's a small risk of infection at the puncture site, which can be minimized by keeping the area clean. Another rare complication is a hematoma, which is a collection of blood under the skin. If you notice excessive bleeding, significant swelling, or signs of infection (like redness, warmth, or pus) at the puncture site, you should contact your doctor.

Frequently asked questions

What is the normal range for ACTH?

The normal range for ACTH can vary slightly between different laboratories. Generally, for a blood sample taken in the morning, a typical adult reference range might be around 6 to 50 picograms per milliliter (pg/mL). Your lab report will usually provide the specific normal range for their tests, and your doctor will interpret your results based on that.

Can stress affect ACTH levels?

Yes, stress can significantly affect ACTH levels. Both physical and emotional stress can stimulate your pituitary gland to release more ACTH, which then causes your adrenal glands to produce more cortisol. This is your body's natural "fight or flight" response. For accurate test results, it's important to be as relaxed as possible during the blood draw.

Is the ACTH test the only test needed to diagnose adrenal problems?

No, the ACTH test is usually just one part of a comprehensive evaluation. Your doctor will typically order other tests, such as blood or urine cortisol tests, and sometimes imaging scans (like MRI or CT scans), to get a complete picture. All these results, along with your symptoms and medical history, help your doctor make an accurate diagnosis.

What's the difference between Cushing's disease and Cushing's syndrome?

Cushing's syndrome is a general term for having too much cortisol in your body, regardless of the cause. Cushing's disease is a specific type of Cushing's syndrome where the excess cortisol is caused by a tumor in the pituitary gland that produces too much ACTH. So, Cushing's disease is a cause of Cushing's syndrome.

How long does it take to get ACTH test results back?

The time it takes to get ACTH test results can vary, but it typically ranges from a few days to about a week. Some specialized labs might take a bit longer. Your doctor's office will usually contact you when your results are ready to discuss them and plan any next steps.

Can certain foods or drinks affect my ACTH test?

While specific foods don't directly alter ACTH levels, fasting is often required before the test. This is because eating can affect other hormones and substances in your blood that might interfere with the overall interpretation of your endocrine system's function. Always follow your doctor's specific fasting instructions.

Sources

• MedlinePlus — Adrenocorticotropic Hormone
• Mayo Clinic — Adrenocorticotropic Hormone
• Cochrane Library — Adrenocorticotropic Hormone