Adrenocorticotropic Hormone (ACTH) Stimulation Test

The Adrenocorticotropic hormone (ACTH) stimulation test is a medical procedure used to assess the functioning of the adrenal glands, specifically their ability to produce cortisol in response to ACTH stimulation.

Purpose

The primary purpose of the ACTH stimulation test is to diagnose and differentiate between various disorders of the adrenal gland, such as:

• Adrenal insufficiency (Addison's disease)
• Adrenal hyperplasia
• Cushing's syndrome
• Congenital adrenal hyperplasia

Procedure

The ACTH stimulation test involves the following steps:

1. A baseline blood sample is drawn to measure the patient's cortisol level.
2. A synthetic form of ACTH, called cosyntropin or tetracosactide, is administered intravenously or intramuscularly.
3. Additional blood samples are drawn at 30 and 60 minutes after ACTH administration to measure the response of cortisol levels.
4. In some cases, a 24-hour urine collection may be performed to measure cortisol excretion.

Interpretation of Results

The results of the ACTH stimulation test are interpreted as follows:

• A normal response is indicated by an increase in cortisol levels after ACTH administration, typically exceeding 18-20 μg/dL at 30 or 60 minutes.
• An abnormal response may indicate adrenal insufficiency or other disorders, such as a failure to increase cortisol levels above 18-20 μg/dL.

Precautions and Contraindications

Certain precautions and contraindications should be considered before performing the ACTH stimulation test:

• Pregnancy or breastfeeding: The test should be performed with caution in pregnant or breastfeeding women, as ACTH may stimulate fetal adrenal production.
• Adrenal crisis: Patients with suspected adrenal crisis should receive emergency treatment before undergoing the test.
• Corticosteroid therapy: Patients on corticosteroid therapy may require temporary discontinuation of medication before the test to ensure accurate results.

Risks and Side Effects

The ACTH stimulation test is generally a safe procedure, but potential risks and side effects include:

• Pain or discomfort at the injection site
• Allergic reactions to cosyntropin or tetracosactide
• Adrenal crisis in patients with untreated adrenal insufficiency

Limitations and Alternatives

The ACTH stimulation test has limitations, including:

• Variability in cortisol response among individuals
• Potential for false-negative results in patients with recent corticosteroid therapy or other medical conditions

Alternative diagnostic tests, such as the insulin tolerance test or glucagon stimulation test, may be used in certain situations.