What to Expect During a Adrenocorticotropic Hormone

The ACTH stimulation test helps doctors check how well your adrenal glands are working by measuring their response to a special hormone. This test involves taking blood samples before and after you receive a synthetic (man-made) version of adrenocorticotropic hormone (ACTH). It helps diagnose conditions where your body might not be making enough cortisol, an important stress hormone.

What is an ACTH stimulation test?

An ACTH stimulation test is a medical procedure that evaluates the function of your adrenal glands, which are small glands located on top of your kidneys. It measures how much cortisol your adrenal glands produce in response to a synthetic version of adrenocorticotropic hormone (ACTH). This test helps doctors understand if your adrenal glands are producing the right amount of cortisol.

Your adrenal glands make several important hormones, including cortisol. Cortisol is vital for many body functions, such as managing stress, controlling blood sugar, and reducing inflammation. The pituitary gland, located at the base of your brain, produces natural ACTH, which signals your adrenal glands to release cortisol. During an ACTH stimulation test, you receive a man-made form of ACTH, often called cosyntropin. This synthetic hormone acts like your body's natural ACTH, prompting your adrenal glands to produce cortisol. By measuring your cortisol levels before and after this stimulation, doctors can assess your adrenal glands' ability to respond and produce cortisol. This test is a key tool for diagnosing conditions related to adrenal gland function. It helps differentiate between various causes of adrenal problems, guiding appropriate treatment. The test is generally safe and well-tolerated by most people. (MedlinePlus, Mayo Clinic)

Why is an ACTH stimulation test ordered?

An ACTH stimulation test is primarily ordered to diagnose or rule out adrenal insufficiency, a condition where your adrenal glands do not produce enough cortisol. It can also help determine if the problem lies with the adrenal glands themselves (primary adrenal insufficiency) or with the pituitary gland, which signals the adrenals (secondary adrenal insufficiency).

Your doctor might order this test if you have symptoms that suggest low cortisol levels. These symptoms can include ongoing fatigue, unexplained weight loss, low blood pressure (hypotension), muscle weakness, and changes in skin color, such as darkening of the skin (hyperpigmentation). These signs can point to conditions like Addison's disease, which is a form of primary adrenal insufficiency. Understanding the cause of adrenal insufficiency is crucial for proper treatment. If the adrenal glands are not responding to ACTH, it suggests a problem with the glands themselves. If they respond, but your natural ACTH levels are low, it might indicate an issue with your pituitary gland's ability to produce ACTH. In some cases, the test might also be used to monitor the function of your adrenal glands if you have been on long-term steroid medications. Steroids can suppress your adrenal glands' natural ability to produce cortisol, and the test can help assess their recovery. (MedlinePlus, Mayo Clinic)

How to prepare

Proper preparation is important for an accurate ACTH stimulation test. Your doctor will provide specific instructions, which often include fasting for several hours before the test and discussing any medications you are currently taking. Certain drugs, like steroids or estrogen, can affect cortisol levels and may need to be temporarily stopped.

You will likely be asked to avoid eating or drinking anything except water for 8 to 12 hours before the test. This is known as fasting. Fasting helps ensure that your body's natural processes do not interfere with the test results. Always follow your doctor's exact instructions regarding fasting. It is crucial to tell your doctor about all medications, supplements, and herbal remedies you are taking. Some medications, such as corticosteroids (like prednisone), estrogen, and spironolactone, can affect your cortisol levels and may need to be paused for a few days or weeks before the test. Do not stop taking any prescribed medication without first talking to your doctor. Your doctor might also advise you to avoid strenuous exercise or excessive stress before the test, as these can temporarily influence cortisol levels. Getting a good night's sleep the day before can also help ensure your body is in a stable state for accurate measurement. (MedlinePlus, Mayo Clinic)

What to expect during

During an ACTH stimulation test, you will typically have two blood samples taken. First, a healthcare professional will draw a blood sample to measure your baseline cortisol level. Then, you will receive an injection of synthetic ACTH. After a waiting period, usually 30 or 60 minutes, a second blood sample will be drawn to see how your cortisol levels have changed.

When you arrive for the test, a nurse or phlebotomist (a person trained to draw blood) will clean a small area on your arm, usually inside your elbow. They will then insert a small needle into a vein to collect the first blood sample. This sample measures your cortisol level before any stimulation, known as your baseline. After the first blood draw, you will receive an injection of cosyntropin, the synthetic ACTH. This injection is usually given into a muscle (intramuscularly) or directly into a vein (intravenously). The injection itself is quick and similar to other shots you might have received. Following the injection, you will wait for a specific amount of time, typically 30 or 60 minutes, depending on the exact protocol your doctor uses. During this time, the synthetic ACTH will stimulate your adrenal glands. After the waiting period, a second blood sample will be drawn from the same or a different vein to measure your stimulated cortisol level. The entire process, including waiting time, usually takes about an hour to an hour and a half. (MedlinePlus, Mayo Clinic)

Understanding your results

Understanding your ACTH stimulation test results requires interpretation by a qualified clinician, who will consider your symptoms and medical history. Generally, a healthy response shows a significant rise in cortisol levels after the ACTH injection. If cortisol levels do not rise adequately, it may indicate adrenal insufficiency, but the specific pattern helps determine the cause.

After the test, your blood samples are sent to a laboratory for analysis. The lab measures the amount of cortisol in both your baseline and stimulated blood samples. Your doctor will then compare these levels to established normal ranges. If your adrenal glands are functioning normally, your cortisol level should significantly increase after the synthetic ACTH injection. For example, a common threshold for a normal response is a stimulated cortisol level above 18-20 micrograms per deciliter (mcg/dL), though specific cut-offs can vary slightly between labs and clinical guidelines. (Mayo Clinic) If your cortisol levels do not rise sufficiently after the injection, it suggests adrenal insufficiency. If your baseline ACTH levels are high, but your adrenals don't respond, it points to primary adrenal insufficiency (a problem with the adrenal glands themselves). If both your baseline ACTH and cortisol are low, and your adrenals don't respond well, it might suggest secondary adrenal insufficiency (a problem with the pituitary gland). Your doctor will explain what your specific results mean for your health. (MedlinePlus, Mayo Clinic)

Risks

The ACTH stimulation test is generally considered safe, with very few risks. The most common risks are minor and related to the blood draw, such as slight pain, bruising, or lightheadedness at the injection site. Serious complications, like allergic reactions to the synthetic ACTH, are rare but possible.

As with any blood test, you might experience some discomfort when the needle is inserted. After the blood draw, you may have a small bruise, mild soreness, or slight bleeding at the site. Rarely, some people might feel dizzy or lightheaded during or after the blood draw. These effects are usually temporary and resolve quickly. Allergic reactions to the synthetic ACTH (cosyntropin) are uncommon. Symptoms of an allergic reaction could include a rash, itching, swelling, or difficulty breathing. If you have a history of allergies, especially to medications, be sure to inform your doctor before the test. Healthcare professionals are trained to recognize and manage such reactions. It is important to discuss any concerns you have about the test with your doctor before it is performed. They can explain the risks and benefits in the context of your individual health. The benefits of accurately diagnosing adrenal conditions usually outweigh these minor risks. (MedlinePlus, Mayo Clinic, Cochrane Library)

Frequently asked questions

Can I eat or drink before an ACTH stimulation test?

No, you will typically need to fast for 8 to 12 hours before an ACTH stimulation test. This means avoiding all food and drinks except water. Always follow your doctor's specific instructions to ensure accurate test results.

Do I need to stop taking my medications before the test?

You might need to stop certain medications, such as corticosteroids or estrogen, before an ACTH stimulation test, as they can affect your cortisol levels. It is crucial to discuss all your medications with your doctor, and never stop taking any prescribed drug without their guidance.

How long does an ACTH stimulation test take?

The entire ACTH stimulation test, including the initial blood draw, the synthetic ACTH injection, and the waiting period for the second blood draw, usually takes about 60 to 90 minutes from start to finish.

Is the ACTH stimulation test painful?

The ACTH stimulation test involves two blood draws and an injection, which may cause brief discomfort, similar to a pinprick. Most people find the test tolerable, and any pain is usually mild and temporary.

What do low cortisol levels after the test mean?

Low cortisol levels after an ACTH stimulation test can indicate adrenal insufficiency, meaning your adrenal glands are not producing enough cortisol. Your doctor will interpret these results in context with your symptoms and other tests to determine the specific cause and type of insufficiency.

Can stress affect my ACTH stimulation test results?

Yes, significant stress can temporarily increase your body's natural cortisol production, which might influence test results. Your doctor may advise you to avoid excessive stress or strenuous activity before the test to help ensure the most accurate readings.

Sources

• MedlinePlus — What to Expect During a Adrenocorticotropic Hormone
• Mayo Clinic — What to Expect During a Adrenocorticotropic Hormone
• Cochrane Library — What to Expect During a Adrenocorticotropic Hormone