Why a Adrenocorticotropic Hormone Is Ordered

An adrenocorticotropic hormone (ACTH) test is ordered to help evaluate how well your adrenal glands and pituitary gland are working. This test measures the amount of ACTH in your blood, a hormone that controls cortisol production. It helps diagnose conditions like Cushing's syndrome or Addison's disease, which involve too much or too little cortisol.

What is Why a Adrenocorticotropic Hormone Is Ordered?

An adrenocorticotropic hormone (ACTH) test measures the level of ACTH in your blood, a hormone produced by your pituitary gland. This test helps doctors understand if your body is making the right amount of cortisol, a stress hormone, and to diagnose conditions affecting your adrenal or pituitary glands.

The adrenocorticotropic hormone (ACTH) test is a blood test that measures the amount of ACTH in your bloodstream. ACTH is a crucial hormone made 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 produce and release cortisol. Cortisol is often called the "stress hormone," but it plays many vital roles in your body. It helps regulate your metabolism, reduce inflammation, control blood sugar levels, and maintain your blood pressure. The pituitary gland and adrenal glands work together in a delicate balance, forming what is known as the hypothalamic-pituitary-adrenal (HPA) axis. When your body needs more cortisol, your pituitary gland releases more ACTH. When cortisol levels are high enough, the pituitary gland reduces ACTH production. The ACTH test helps your doctor check if this communication system is working correctly and if your body is producing appropriate levels of these hormones. An imbalance can point to various health conditions affecting either the pituitary or adrenal glands.

Why it's ordered

Your doctor orders an ACTH test to investigate symptoms suggesting an imbalance in cortisol levels, such as unexplained weight changes, muscle weakness, or fatigue. It helps diagnose conditions like Cushing's syndrome (too much cortisol) or Addison's disease (too little cortisol), and to determine if the problem lies with your pituitary or adrenal glands.

The ACTH test is primarily ordered when your doctor suspects you have a condition that causes either too much or too little cortisol in your body. Symptoms that might prompt this test include unexplained weight gain or loss, high blood pressure (hypertension), muscle weakness, skin changes, or persistent fatigue. One common reason for the test is to diagnose Cushing's syndrome, a condition where your body produces too much cortisol. This can be caused by a tumor in the pituitary gland (Cushing's disease), a tumor in the adrenal gland, or a tumor elsewhere in the body that produces ACTH (ectopic ACTH syndrome). The ACTH test helps differentiate between these causes. Conversely, the test is also used to diagnose adrenal insufficiency, where your adrenal glands do not produce enough cortisol. This can be primary adrenal insufficiency, also known as Addison's disease, where the adrenal glands themselves are damaged. It can also be secondary adrenal insufficiency (hypopituitarism), where the pituitary gland doesn't make enough ACTH to stimulate the adrenal glands. The ACTH test helps determine if the problem originates in the adrenal glands or the pituitary gland.

How to prepare

Preparing for an ACTH test usually involves fasting for several hours before the blood draw, often overnight. You may also need to avoid certain medications, such as corticosteroids, which can affect results. Your doctor will provide specific instructions, including the best time for the test, as ACTH levels change throughout the day.

Proper preparation is crucial for accurate ACTH test results. Your doctor will typically instruct you to fast for 8 to 12 hours before the blood test, meaning you should not eat or drink anything except water during that time. It's important to follow these instructions carefully. Certain medications can interfere with ACTH levels and should be avoided before the test, if medically safe to do so. These may include corticosteroids (like prednisone), estrogen, amphetamines, insulin, and spironolactone. Always discuss all medications, supplements, and herbal remedies you are taking with your doctor, as they will advise you on which ones to stop and for how long. Timing of the test is also very important. ACTH levels naturally fluctuate throughout the day, typically being highest in the early morning (between 6 a.m. and 8 a.m.) and lowest in the late evening. For this reason, your doctor will usually schedule your blood draw for the morning to capture peak levels and ensure consistent, comparable results. Stress can also temporarily affect hormone levels, so try to remain calm and relaxed before the test.

What to expect during

During an ACTH test, a healthcare professional will draw a small sample of blood, typically from a vein in your arm. The process is quick, usually taking only a few minutes, and is similar to any standard blood test. You might feel a brief pinch or sting as the needle is inserted.

The ACTH test is a routine blood draw, similar to many other blood tests you may have had. A healthcare professional, such as a nurse or phlebotomist, will perform the procedure. You will typically be seated comfortably, and they will ask you to extend your arm. First, they will clean the skin around the chosen vein, usually on the inside of your elbow, with an antiseptic wipe. They may then tie an elastic band (tourniquet) around your upper arm to make the vein more visible and easier to access. Once a suitable vein is found, a small needle will be inserted into the vein to collect a blood sample into a tube. After enough blood has been collected, the tourniquet will be removed, and then the needle will be withdrawn. A small piece of gauze or cotton will be pressed onto the puncture site, and a bandage will be applied. The entire process usually takes only a few minutes. You might feel a brief pinch or sting when the needle goes in, and some mild throbbing or bruising afterward is common.

Understanding your results

Understanding your ACTH test results involves your doctor interpreting them alongside your cortisol levels and other clinical findings. High ACTH with low cortisol may suggest primary adrenal insufficiency (Addison's disease), while low ACTH with low cortisol could indicate a pituitary problem. High ACTH with high cortisol might point to Cushing's disease or ectopic ACTH production.

Interpreting ACTH test results is complex and requires a qualified clinician to consider them in the context of your symptoms, medical history, and other diagnostic tests, especially cortisol levels. Normal ranges for ACTH can vary slightly between different laboratories. Generally, if your ACTH levels are high but your cortisol levels are low, it often suggests primary adrenal insufficiency (Addison's disease). This means your adrenal glands are not producing enough cortisol, even though your pituitary gland is sending strong signals (high ACTH) to try and stimulate them. If both your ACTH and cortisol levels are low, it may indicate secondary adrenal insufficiency, where the pituitary gland is not producing enough ACTH to stimulate the adrenal glands. Conversely, if both your ACTH and cortisol levels are high, it could point to Cushing's disease, caused by an ACTH-producing tumor in the pituitary gland, or ectopic ACTH syndrome, where a tumor elsewhere in the body is producing ACTH. If your ACTH levels are low but your cortisol levels are high, it might suggest an adrenal tumor that is overproducing cortisol independently. This information is for general understanding only; your doctor will explain what your specific results mean for your health.

Risks

The risks associated with an ACTH blood test are minimal and similar to those of any routine blood draw. These may include slight pain or bruising at the needle site, or, rarely, dizziness or infection. Serious complications are very uncommon, and the benefits of diagnosis usually outweigh these minor risks.

An ACTH blood test is considered a very safe procedure, with risks comparable to any standard blood draw. The most common side effects are usually mild and temporary. You might experience some slight pain or tenderness at the site where the needle was inserted. Bruising is also common at the puncture site. To minimize bruising, you can apply gentle pressure to the area for a few minutes after the bandage is applied. Less common risks include feeling lightheaded or dizzy, especially if you are sensitive to blood draws, or, very rarely, fainting. Infection at the puncture site is extremely rare, as healthcare professionals follow strict sterile procedures. Excessive bleeding is also uncommon but can occur in individuals with bleeding disorders or those taking blood-thinning medications. Always inform your healthcare provider if you have any concerns or a history of these issues. For most people, the diagnostic information gained from an ACTH test far outweighs these minor potential risks.

Frequently asked questions

What is the difference between ACTH and cortisol?

ACTH (adrenocorticotropic hormone) is a hormone made by your pituitary gland that acts as a messenger, telling your adrenal glands to produce cortisol. Cortisol is a steroid hormone made by your adrenal glands that carries out many important functions, such as helping your body respond to stress, regulating blood sugar, and reducing inflammation.

Why is the ACTH test usually done in the morning?

The ACTH test is usually done in the morning because ACTH levels naturally fluctuate throughout the day, typically being highest between 6 a.m. and 8 a.m. and lowest in the evening. Testing at a consistent time helps ensure accurate and comparable results, reflecting the body's normal daily rhythm.

Can stress affect my ACTH test results?

Yes, stress can affect your ACTH test results. Both physical and emotional stress can cause your body to release more ACTH and cortisol, potentially leading to temporarily elevated levels. It's important to try and be as relaxed as possible before and during the test, and to inform your doctor about any significant stress you are experiencing.

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

The time it takes to get ACTH test results back can vary depending on the laboratory. Generally, results are available within a few business days. Your doctor's office will contact you when your results are ready and will explain what they mean in the context of your overall health and symptoms.

What happens if my ACTH levels are abnormal?

If your ACTH levels are abnormal, your doctor will likely order additional tests to pinpoint the exact cause of the imbalance. This might include further blood tests, urine tests, or imaging scans of your pituitary or adrenal glands. Abnormal ACTH levels indicate an imbalance that needs further investigation to determine the correct diagnosis and treatment plan.

Are there any medications that interfere with the ACTH test?

Yes, several medications can interfere with ACTH test results. These include corticosteroids (like prednisone), estrogen, amphetamines, insulin, and spironolactone. It is crucial to inform your doctor about all medications, supplements, and herbal remedies you are taking, as they may instruct you to temporarily stop certain ones before the test.

Sources

• MedlinePlus — Why a Adrenocorticotropic Hormone Is Ordered
• Mayo Clinic — Why a Adrenocorticotropic Hormone Is Ordered
• Cochrane Library — Why a Adrenocorticotropic Hormone Is Ordered