What is this test?
ACTH is a pituitary hormone that signals the adrenal glands to produce cortisol.
Why might it be ordered?
- To determine whether an abnormality in cortisol may be related to the pituitary or adrenal glands.
- When following an established disorder in this hormonal system.
What sample is needed?
Venous blood is taken for plasma. The sample requires rapid and correct laboratory processing.
How should you prepare?
Time is important and usually agrees with a cortisol measurement. Report steroid medications, including inhalers, creams, and injections. Tell the laboratory about all medicines, hormone treatments, vitamins and supplements you take. Do not stop or change treatment unless your clinician tells you to. Follow any instructions about fasting and the time of collection.
How should you understand the result?
ACTH is interpreted with cortisol and sometimes dynamic testing. A single value cannot identify the location or cause of a problem on its own. Your result is interpreted using the reference interval on the laboratory report and in the context of your symptoms, medical history and other test findings.
Sources and editorial status
This patient-facing text is an editorial draft. It should be approved by a laboratory physician before official publication.