Adrenocorticotropic Hormone (ACTH)

Adrenocorticotropic Hormone (ACTH) Test: Details & Precautions

The Adrenocorticotropic Hormone (ACTH) test measures the level of ACTH in the blood, which is produced by the pituitary gland to stimulate the adrenal glands to produce cortisol. Cortisol is essential for stress response, metabolism, immune function, and blood pressure regulation.

Test Details

✅ Purpose:

• Diagnoses adrenal and pituitary disorders, including:
  • Cushing’s disease/syndrome (high cortisol).
  • Addison’s disease (adrenal insufficiency) (low cortisol).
  • Secondary adrenal insufficiency (pituitary gland dysfunction).
  • Ectopic ACTH production (tumors producing ACTH).
• Evaluates unexplained weight gain, weakness, fatigue, or blood pressure issues.

✅ Normal Reference Range (May vary by lab):

• Morning (8 AM): 10–60 pg/mL (picograms per milliliter).
• Evening (4 PM): Less than 20 pg/mL.
• Higher levels may indicate Cushing’s disease, Addison’s disease, or ectopic ACTH syndrome.
• Lower levels may suggest adrenal insufficiency or pituitary dysfunction.

Precautions Before & During the Test

🔹 Before the Test

1️⃣ Time-Sensitive Test

• ACTH follows a circadian rhythm:
  • Highest in the morning (6–8 AM).
  • Lowest in the evening (6–11 PM).
• Doctors typically request a morning test for accurate results.

2️⃣ Fasting & Dietary Considerations

• Some labs require fasting (8–12 hours before the test).
• Avoid excessive sugar and caffeine before the test.

3️⃣ Medication Restrictions (Consult doctor before stopping medications)

• Steroid medications (e.g., prednisone, dexamethasone, hydrocortisone) can alter results.
• Birth control pills, diuretics, and certain antidepressants can affect ACTH levels.

4️⃣ Physical & Emotional Factors

• Stress, pain, and exercise can temporarily increase ACTH.
• Try to stay relaxed before the test.

🔹 During the Test

• Blood Sample Collection:
  • A blood sample is drawn from a vein, typically in the morning.
  • In some cases, a plasma cortisol test is done alongside ACTH for better diagnosis.

🔹 After the Test

• Results take a few days.
• If abnormal, additional tests may be required:
  • Cortisol test (serum or saliva).
  • ACTH stimulation test (for adrenal insufficiency).
  • Dexamethasone suppression test (for Cushing’s syndrome).
  • Imaging (MRI or CT scan of the pituitary or adrenal glands).

Interpreting Results

📉 Low ACTH Levels May Indicate:

• Adrenal Tumors (Cortisol-Secreting Tumor) → High cortisol suppressing ACTH.
• Pituitary Dysfunction (Secondary Adrenal Insufficiency).
• Excessive Steroid Use (Cushing’s Syndrome due to steroids).

📈 High ACTH Levels May Indicate:

• Addison’s Disease (Primary Adrenal Insufficiency) → Adrenal glands fail to produce cortisol.
• Cushing’s Disease (Pituitary ACTH Overproduction) → Leads to high cortisol.
• Ectopic ACTH Syndrome (e.g., Lung Cancer Tumors Producing ACTH).
• Chronic Stress or Depression.