Hormones

ACTH (Adrenocorticotropic Hormone)

The pituitary releases ACTH, which tells the adrenal glands to make cortisol. When cortisol rises, ACTH is suppressed, and vice versa. Measuring both from the same sample shows whether a problem sits in the adrenal glands or in the pituitary. ACTH varies considerably across the day and is highest in the early morning.

Why Test ACTH?

The test is used when adrenal insufficiency (Addison's disease) is suspected, and when investigating excess cortisol (Cushing's syndrome). It is always taken together with cortisol and interpreted by a doctor, often as part of a wider assessment that includes stimulation testing.

What Do High ACTH Levels Mean?

A high ACTH with a low cortisol indicates primary adrenal insufficiency, meaning the adrenal glands are not responding. A high ACTH with a high cortisol is seen with ACTH-producing tumours, most often in the pituitary. Severe stress and acute illness also raise ACTH temporarily.

What Do Low ACTH Levels Mean?

A low ACTH with a low cortisol indicates the pituitary is not signalling as it should, for example after prolonged corticosteroid treatment or with disease of the pituitary. A low ACTH with a high cortisol indicates the adrenal glands are producing too much on their own.

Symptoms to Watch For

  • Marked fatigue that does not improve with rest
  • Dizziness on standing and low blood pressure
  • Weight loss and loss of appetite
  • Darker skin, particularly in creases and scars
  • Craving for salt
  • Nausea and abdominal discomfort

Who Should Get Tested?

  • People being investigated for adrenal insufficiency or excess cortisol
  • People with an abnormal cortisol result
  • People on long-term corticosteroid treatment with symptoms as the dose is reduced
  • People with known disease of the pituitary gland

How to Prepare for Your Test

The test is taken in the morning, usually between 07:00 and 09:00, because the level varies across the day. The sample is fragile and must be chilled and handled quickly, so call the sampling location in advance. Never stop corticosteroid treatment before a test without speaking to your doctor. Bring valid ID.

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ACTH (Adrenocorticotropic Hormone) →

Frequently Asked Questions

What time of day should ACTH be taken?
In the morning, usually between 07:00 and 09:00, when the level is highest. A sample taken later in the day is difficult to interpret.
Do I need to fast for the ACTH test?
No, fasting is not normally required. The time of day matters, as does being rested and calm at the appointment.
Can stress affect the result?
Yes. Acute physical or psychological stress, illness and lack of sleep raise ACTH temporarily. The value is therefore always interpreted alongside cortisol and your circumstances.
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Wellth

Our content is written and reviewed by Wellth, and fact-checked against peer-reviewed research and current Swedish clinical guidelines.

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Medical Disclaimer

The information on this page is provided for informational purposes only and does not constitute professional medical advice, diagnosis, or treatment. Wellth provides health information and testing services but is not a substitute for clinical care. Always consult a qualified healthcare provider if you have questions about a medical condition. If you are experiencing severe or urgent symptoms, contact your doctor or call 1177 Vårdguiden. Blood test results should be interpreted by a qualified healthcare professional in the context of your complete medical history.