Adrenocorticotropic Hormone (ACTH)

Adrenocorticotropic Hormone (ACTH) – What It Means in Your Lab Results

Adrenocorticotropic Hormone (ACTH) is a critical hormone produced by the pituitary gland in the brain. Its main job is to signal your adrenal glands, located on top of the kidneys, to release cortisol — the body’s key stress hormone.

ACTH plays a central role in your body's hypothalamic-pituitary-adrenal (HPA) axis, which regulates your response to stress, blood sugar levels, metabolism, immune response, and more.

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Why ACTH Is Measured

An ACTH blood test is commonly ordered when:

• Cortisol levels are abnormal

• Symptoms suggest adrenal insufficiency or Cushing’s syndrome

• You're being evaluated for pituitary gland function

• You’re undergoing an ACTH stimulation test (Cosyntropin test) and a baseline ACTH is needed

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How ACTH Works in the Body

When your brain senses that your body needs more cortisol:

1. The hypothalamus releases CRH (corticotropin-releasing hormone)

2. CRH signals the pituitary gland to release ACTH

3. ACTH travels through your blood to the adrenal glands

4. The adrenal glands respond by producing and releasing cortisol

This feedback loop helps your body maintain balance during physical, emotional, and metabolic stress.

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What High or Low ACTH Levels May Indicate

High ACTH Levels may suggest:

• Primary adrenal insufficiency (Addison’s disease) – the adrenal glands aren’t producing enough cortisol, so the pituitary increases ACTH in compensation

• Ectopic ACTH production – sometimes seen in certain tumors (e.g., small-cell lung cancer)

• Congenital adrenal hyperplasia

• Stress, including severe illness or surgery

Low ACTH Levels may suggest:

• Secondary adrenal insufficiency – due to pituitary gland dysfunction or suppression (often from long-term steroid use)

• Cushing’s syndrome due to adrenal overproduction of cortisol (which suppresses ACTH through feedback)

• Hypopituitarism (underactive pituitary)

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Sample Type and Handling

• Sample type: Plasma

• Collection tube: Chilled lavender-top (EDTA) tube

• Special handling: Must be kept on ice and processed promptly due to ACTH's instability

This test is often paired with serum cortisol for more accurate interpretation.

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Final Thoughts

ACTH is a key marker in evaluating adrenal and pituitary health. It provides essential insight into whether your adrenal glands are functioning properly — and if not, whether the issue is coming from the adrenals themselves or the brain. When interpreted alongside cortisol levels, ACTH results help doctors diagnose conditions like Addison’s disease, Cushing’s syndrome, or secondary adrenal insufficiency.

If your ACTH levels are outside the normal range, follow up with your healthcare provider for further testing and clinical evaluation.