Test Overview
Chemiluminescence Assay
Knowledge of ACTH levels in addition to serum cortisol and urinary free cortisol is useful in the differential diagnosis of Cushing's syndrome, ectopic ACTH syndrome (e.g., carcinoma of lung, islet cell tumors, carcinoid tumors, medullary carcinoma of thyroid), Addison's disease by hypopituitarism and ACTH-producing pituitary tumors (e.g., Nelson's syndrome).
5 - 52 pg/mL
* Reference ranges may change over time. Please refer to the original patient report when evaluating results.
The ACTH level may be elevated by stress, and is subject to diurnal variation. In normal individuals with a daytime pattern of activities, ACTH levels reach a peak between 6:00AM - 8:00AM. Glucocorticoid therapy will depress ACTH.
ACTH measurement is not recommended for patients who have been administered cosyntropin (ACTH (1-24)) because the results may be falsely elevated or depressed.
Test Details
8 hours
- ACTH
- Adrenal Corticotropin
- Corticotropin
Specimen Requirements
Collect specimen in a chilled lavender top tube. Deliver to laboratory on ice within in 30 minutes or centrifuge immediately, aliquot plasma into plastic vial, freeze within 1 hour of collection, and transport frozen on dry ice.
Collect in prechilled tube and place on ice immediately. Must arrive in lab or aliquot and freeze within 30 minutes.
Additional Information
ACTH is unstable in blood. Improper processing or storage may result in erroneously low levels of ACTH. ACTH levels in pituitary dependent Cushing's disease may be elevated or high normal (inappropriately elevated for the time of the day). ACTH levels in ectopic ACTH syndrome are usually quite high, whereas in Cushing's syndrome due to adrenal adenoma or carcinoma ACTH levels are very low to undetectable. Pituitary dependent Cushing's disease (i.e., pituitary ACTH hypersecretion) usually demonstrates reduced or lack of ACTH suppression by low-dose dexamethasone (2 mg q 6 hours for 24 hours) and reduced or normal suppression of ACTH by high dose dexamethasone (8 mg q 6 hours for 24 hours). Cushing's syndrome due to ectopic ACTH production is not usually suppressed by either low- or high-dose dexamethasone. Hypopituitarism with ACTH deficiency does not respond to provocative testing (e.g. hypoglycemia or metyrapone administration) with the expected increase in plasma ACTH concentration. In primary adrenal insufficiency (Addison's disease) and in Nelson's syndrome, plasma concentrations of ACTH are consistently elevated. For sequential follow-up, plasma ACTH samples should always be drawn at the same time each day, most preferably at 8:00am.