ACTH (adrenocorticotropic hormone)
Pituitary hormone that signals the adrenal glands to make cortisol
Also known as
Definition
ACTH (adrenocorticotropic hormone, corticotropin) is made in the pituitary gland and signals the adrenal glands to release cortisol. Through a feedback loop with the hypothalamus, ACTH rises when cortisol is low and falls when cortisol is high. The blood test is therefore usually done together with cortisol to narrow down disorders of the pituitary and adrenal glands.
| Parameter | Value |
|---|---|
| Unit | pg/ml or pmol/l |
| Reference Range | Early-morning blood draw: 9–52 pg/ml (about 2–11.5 pmol/l). Labs differ; the range printed on your report is what counts, and your doctor interprets the result. |
Agree on your personal target range with your doctor.
Conversion: 1 pg/ml ≈ 0.22 pmol/l. ACTH varies over the day and is highest in the early morning; values taken at other times are only partly comparable with this range.
↓ What a low value means
According to MedlinePlus, a low ACTH level is most often related to taking glucocorticoids (corticosteroid medicines), which suppress the body's own ACTH production. Other possible links are an underactive pituitary gland or a cortisol-producing tumor of the adrenal gland. The value only becomes meaningful together with cortisol. Discuss any deviation with your doctor.
↑ What a high value means
A high ACTH level can be related to adrenal insufficiency (Addison disease): the adrenal glands make too little cortisol, so the pituitary releases more ACTH. Other possible causes are a usually benign ACTH-producing pituitary tumor (Cushing disease), rare ACTH-producing tumors outside the pituitary, congenital adrenal hyperplasia or multiple endocrine neoplasia. Which explanation applies only becomes clear from cortisol and further tests; discuss the result with your doctor.
When to test
The test is usually ordered after an abnormal cortisol result or when symptoms point to too much or too little cortisol, such as lasting fatigue, weight loss and muscle weakness, or weight gain with a round face and easy bruising. Blood is usually drawn early in the morning, fasting if instructed. Glucocorticoids such as prednisone, hydrocortisone or dexamethasone can affect the result; never stop medicines without talking to your doctor.
Frequently asked questions
Why is ACTH measured together with cortisol? +
ACTH and cortisol regulate each other, so only the combination shows where a problem might lie. According to MedlinePlus, high ACTH with low cortisol points more toward an adrenal problem, while low ACTH with high cortisol points more toward a cortisol source such as steroid medicines or an adrenal tumor.
Why is blood drawn in the morning? +
ACTH follows a daily rhythm and is highest in the early morning. To keep values comparable and matched to the reference range, blood is usually drawn early in the morning.
What is the difference between Cushing disease and Cushing syndrome? +
In Cushing syndrome, the body is exposed to too much cortisol over a long period, for example from high-dose steroid medicines or tumors. Cushing disease is the form in which a usually benign pituitary tumor makes too much ACTH.
Can corticosteroid medicines change the result? +
Yes. Glucocorticoids such as prednisone, hydrocortisone or dexamethasone suppress ACTH production; according to MedlinePlus, this is the most common cause of a low ACTH level. Tell your doctor what you take before the test and do not stop anything on your own.
ACTH (adrenocorticotropic hormone)
Sources
Last updated: October 05, 2026
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.