Special Precautions/Comments:

Samples should reach the laboratory within 6hrs of collection.

ACTH concentrations show diurnal variation with high levels in the morning and low levels in the evening. Therefore, as with cortisol, it is important to know the collection time of the plasma sample for interpretation (ideally close 9 am).

Additional Information:

Adrenocorticotropic hormone or corticotropin is a peptide hormone consisting of 39 amino acids. It is produced in the anterior pituitary of the brain as part of the precursor molecule pro‑opiomelanocortin (POMC).  Tissue-specific cleavage results in ACTH and a range of related peptides.

Adrenocorticotropic hormone (ACTH) measurements, performed with this assay in human plasma, are useful as an aid in diagnosis of disorders of the pituitary or adrenal glands, including Cushing’s disease, ectopic ACTH syndrome, autonomous ACTH-producing pituitary tissue (e.g. Nelson’s syndrome) and adrenal insufficiency.

In case of adrenal insufficiency (insufficient production of glucocorticoids or mineralocorticoids from the adrenal glands), basal morning cortisol and ACTH levels can be measured, and an ACTH stimulation test performed, to establish the diagnosis and distinguish between primary adrenal insufficiency (Addison’s disease) and central adrenal insufficiency (secondary or tertiary).

Plasma ACTH measurements are useful in the differential diagnosis of Cushing syndrome aetiology (to differentiate ACTH-dependent from ACTH-independent hypercortisolism). Normal or high ACTH levels in a patient with sustained hypercortisolism, suggest ACTH-dependent cortisol secretion.

The great majority of these patients have Cushing’s disease, in which ACTH hypersecretion is due to an ACTH-secreting pituitary adenoma.

More rarely, high ACTH levels are caused by ectopic ACTH syndrome (EAS), in which ACTH is released by non-pituitary tumours. The most prevalent tumours of EAS are small cell carcinomas of the lung and bronchial carcinoids, but also, less commonly, tumours originating in the thymus, pancreas, and thyroid.