ACTH

10 mL blood in chilled EDTA tube; plasma separated and frozen immediately. Collect sample between 0800-0900 h.

Immunoassay.

< 10 pmol/L (dependent on time of collection).

Investigation of the aetiology of corticosteroid excess or deficiency, as a baseline or as part of a suppression test (eg, Dexamethasone suppression test-long, Dexamethasone suppression test-overnight, in conjunction with Cortisol and/or Cortisol urine).

See Cushing's syndrome and Adrenocortical insufficiency. 

Corticosteroid excess may be associated with high ACTH levels (ectopic or pituitary source) or low levels (adrenal tumour).

Corticosteroid deficiency may be associated with high ACTH levels (primary adrenal insufficiency) or low levels (pituitary deficiency).