ACTH levels in the blood are measured to help detect, diagnose, and monitor conditions associated with excessive or deficient cortisol in the body.
ACTH, the primary stimulator of adrenal cortisol production, is synthesized by the pituitary in response to corticotropin-releasing hormone (CRH), which is released by the hypothalamus.Plasma ACTH and cortisol levels exhibit peaks (6-8am) and nadirs (11pm)
Disorders of cortisol production include:
- Excess cortisol that is due to an ACTH-producing tumour in the pituitary gland (usually a benign tumour)
- Refers to the symptoms and signs associated with excess exposure to cortisol.
In addition to Cushing′s disease, Cushing′s syndrome may be due to an adrenal tumour, adrenal hyperplasia, the use of steroid medications, or due to an ACTH-producing tumour that is located outside the pituitary (such as in the lungs).
- Primary adrenal insufficiency: decreased cortisol production due to adrenal gland damage.
- Secondary adrenal insufficiency: decreased cortisol production because of pituitary dysfunction Hypopituitarism pituitary dysfunction or damage that leads to decreased (or no) hormone production by the pituitary – including ACTH production.
Measuring both ACTH and cortisol can help to differentiate among some of these conditions. Because the level of ACTH normally changes in the opposite direction to the level of cortisol.
0 – 47 ng/L (sample taken at 9am)
Ideally take samples between 9am and 10am.
A 5mL plasma (EDTA) sample is required for analysis. If the ACTH is required as part of a synacthen test then an EDTA sample should be sent at baseline.
ACTH on short synacthen test should only be referred if the 30 min cortisol is less than 500 nmol/L.
Additional information on this test can be found at Lab Tests Online.
Biochemistry Lab, James Cook University Hospital, Marton Road, TS4 3BW