ACTH Stimulation Test: Diagnosing Adrenal Insufficiency

What Is the ACTH Stimulation Test?

The ACTH stimulation test, also known as the cosyntropin stimulation test, is a diagnostic procedure that assesses the functioning of your adrenal glands. This test measures your body's ability to respond to adrenocorticotropic hormone (ACTH), a hormone produced by the pituitary gland that stimulates the adrenal glands to release cortisol. By evaluating cortisol levels before and after an injection of synthetic ACTH, the test helps diagnose adrenal insufficiency, a condition where the adrenal glands fail to produce enough cortisol. The ACTH stimulation test is a crucial tool in determining whether your adrenal glands are responding appropriately to hormonal signals.

Why ACTH Stimulation Test is Done?

The primary reason for undergoing an ACTH stimulation test is to diagnose adrenal insufficiency. This test helps differentiate between primary adrenal insufficiency (Addison's disease), caused by adrenal gland dysfunction, and secondary adrenal insufficiency, resulting from pituitary gland problems that lead to low ACTH production.

Additionally, the ACTH stimulation test is used to assess adrenal reserve in patients with suspected pituitary or hypothalamic disorders, evaluate abnormal cortisol levels found in other tests, and guide treatment decisions involving corticosteroid therapy. By accurately diagnosing the cause of adrenal insufficiency, the ACTH stimulation test enables healthcare providers to develop targeted treatment plans.

How does an ACTH stimulation test work?

The ACTH stimulation test, or cosyntropin stimulation test, involves measuring your cortisol levels at baseline and after administering synthetic ACTH (cosyntropin), usually through an intramuscular or intravenous injection. The test typically follows these steps:

• A baseline blood sample is collected to measure your initial cortisol level
• Synthetic ACTH is injected to stimulate your adrenal glands to release cortisol
• Additional blood samples are taken 30 and/or 60 minutes after the injection to assess your cortisol response

In a person with properly functioning adrenal glands, cortisol levels should significantly increase after ACTH stimulation. If cortisol levels remain low or fail to rise adequately, it suggests adrenal insufficiency.

Types of ACTH Stimulation Tests

There are two main types of ACTH stimulation tests: the standard/high-dose test and the low-dose test.

The standard/high-dose test involves administering 250 micrograms of synthetic ACTH, which is sufficient to maximally stimulate adrenal cortisol production. It is commonly used for diagnosing primary adrenal insufficiency.

The low-dose test uses 1 microgram or less of synthetic ACTH, aiming to detect subtle secondary adrenal insufficiency by mimicking normal physiological ACTH levels. This test may be more sensitive in identifying mild or early pituitary-related insufficiency.

How to Prepare for the ACTH Stimulation Test

To ensure accurate ACTH stimulation test results, proper preparation is essential. Fast for at least 6 hours before the test, you may drink water. Schedule the test early in the morning to align with your body's natural cortisol rhythm. Inform your healthcare provider about any medications you are taking, especially corticosteroids, as they can affect the test results. Stay hydrated, but avoid eating after midnight on the night before the test. Wear comfortable clothing and consider bringing entertainment, as the test can last up to two hours.

What to Expect During the ACTH stimulation test Procedure

During the ACTH stimulation test procedure, you can expect a healthcare professional to draw a baseline blood sample to measure your initial cortisol levels. Synthetic ACTH (cosyntropin) will be administered through an intramuscular or intravenous injection. Additional blood samples will be collected 30 to 60 minutes after the injection to assess your cortisol response.

The procedure is relatively simple and typically painless, apart from minor discomfort from the blood draws and injection. The entire process, including preparation and waiting periods, usually lasts about two hours.

How Long Does the Test Take?

The ACTH stimulation test typically takes around two hours from start to finish. This includes the initial blood draw, administration of synthetic ACTH, and collection of subsequent blood samples at intervals of 30 and 60 minutes post-injection. The test duration allows for adequate time to monitor your adrenal response and ensures accurate cortisol measurement for a comprehensive evaluation of your adrenal function.

What are the risks of an ACTH stimulation test?

The ACTH stimulation test is generally safe, with minimal risks. Possible side effects include minor pain or bruising at the injection site, discomfort from blood draws, or rare allergic reactions to synthetic ACTH. Due to the hormone stimulation involved, the cosyntropin stimulation test should be used cautiously in patients with known hypersensitivity or certain adrenal tumours. However, when performed under medical supervision, the ACTH stimulation test is considered a low-risk procedure.

Normal Range for ACTH Stimulation Test

The ACTH stimulation test normal range varies slightly among laboratories, but generally, a normal response is characterised by a cortisol level that rises to at least 18-20 μg/dL (497-552 nmol/L) 30 or 60 minutes after ACTH administration. In a healthy individual, cortisol levels typically double or triple from the baseline value.

It's important to note that the interpretation of ACTH stimulation test results depends on various factors, such as age, sex, and medical history. Your healthcare provider will consider these factors along with your symptoms and other test results to make an accurate diagnosis and determine the most appropriate course of treatment.

What Do Abnormal Results Mean?

Abnormal ACTH stimulation test results can indicate adrenal insufficiency or other adrenal gland disorders. If your cortisol levels fail to rise adequately after ACTH administration, it suggests that your adrenal glands are not responding properly to stimulation. In primary adrenal insufficiency (Addison's disease), both baseline and stimulated cortisol levels are typically low. In secondary adrenal insufficiency, baseline cortisol may be low or normal, but the response to ACTH stimulation is diminished.

Abnormal results may also be seen in conditions such as congenital adrenal hyperplasia, adrenal tumours, or pituitary disorders. Your healthcare provider will interpret the results in the context of your overall health and may recommend additional tests to confirm the diagnosis.

Factors That Can Influence Test Results

Several factors can influence ACTH stimulation test results, including medications, especially corticosteroids or hormone therapies; stress or illness; recent surgery or trauma; pregnancy; or time of day (cortisol levels are highest in the morning).

To ensure accurate results, it's crucial to inform your healthcare provider about any medications you are taking and follow their instructions for test preparation.

Benefits of the ACTH Stimulation Test

The ACTH stimulation test offers several benefits:

• Helps differentiate between primary and secondary adrenal insufficiency
• Provides valuable information for guiding treatment decisions
• Enables early detection and management of adrenal disorders
• Offers a safe and reliable diagnostic tool for assessing adrenal function

ACTH Test vs. Other Adrenal Function Tests

While the ACTH stimulation test is a commonly used diagnostic tool for adrenal insufficiency, other adrenal function tests may be employed depending on the clinical situation. These include:

• Insulin Tolerance Test (ITT): This test assesses the response of the hypothalamic-pituitary-adrenal axis to induced hypoglycaemia.
• CRH Stimulation Test: This test evaluates the pituitary gland's ability to produce ACTH in response to corticotropin-releasing hormone (CRH) stimulation.
• Adrenal Vein Sampling: This invasive procedure involves collecting blood samples directly from the adrenal veins to measure cortisol and aldosterone levels.

The choice of test depends on the patient's specific symptoms, medical history, and the suspected underlying condition.

When to Consult a Doctor

If you experience symptoms suggestive of adrenal insufficiency, such as chronic fatigue, unexplained weight loss, low blood pressure, skin darkening (hyperpigmentation), salt cravings, abdominal pain, or muscle or joint pain.

It's essential to consult a doctor for a proper evaluation. They may recommend an ACTH stimulation test to assess your adrenal function and determine the underlying cause of your symptoms, enabling prompt diagnosis and appropriate treatment.

Final Thoughts

The ACTH stimulation test is a valuable diagnostic tool for assessing adrenal function and identifying adrenal insufficiency. By understanding the ACTH stimulation test uses, procedure, and interpretation of this test, you can take an active role in your health management. If you suspect adrenal insufficiency, don't hesitate to discuss your concerns with your doctor and explore the benefits of an ACTH stimulation test at a trusted healthcare provider like Metropolis Healthcare.

FAQs

What is the purpose of the ACTH stimulation test?

The ACTH stimulation test evaluates how well your adrenal glands respond to adrenocorticotropic hormone (ACTH). It helps diagnose adrenal insufficiency, such as Addison’s disease, or check pituitary function.

Is the test painful?

The test involves a few blood draws and an injection of synthetic ACTH. While the needle pricks may cause slight discomfort, the procedure is generally not painful.

How long do results take?

Results are usually available within a few days, though this can vary depending on the lab. Your healthcare provider will follow up to discuss the findings.

What do low cortisol levels indicate?

Low cortisol after ACTH injection may suggest adrenal insufficiency. This means the adrenal glands aren’t producing enough cortisol, which could be due to Addison’s disease or pituitary issues.

Can I eat or drink before the test?

You may be asked to fast for 8 hours before the test. Follow your healthcare provider’s instructions closely, and inform them of any medications you’re taking.

What if my results are abnormal?

If your results are below or above ACTH stimulation test normal range, your doctor may order additional hormone tests, imaging, or refer you to an endocrinologist for diagnosis and treatment planning.

Is this test done for Addison’s disease?

Yes, it is a key diagnostic tool for Addison’s disease. It helps assess if your adrenal glands are functioning properly and responding to ACTH.

How often do I need an ACTH stimulation test?

The frequency depends on your condition. For chronic adrenal disorders, periodic testing may be needed to monitor adrenal function or medication effectiveness.

Can stress impact the test results?

Yes, severe stress can affect cortisol levels. Let your doctor know if you’re experiencing acute stress, illness, or sleep deprivation before testing.