ADRENOCORTICOTROPHIC HORMONE (ACTH) - plasma

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Specimen: 10 mL blood in chilled EDTA tube; plasma separated and frozen immediately.

Method: Immunoassay.

Reference Interval: <50 ng/L (dependent on time of collection).

Application: Investigation of the aetiology of corticosteroid excess or deficiency, as a baseline or as part of a suppression test (eg dexamethasone), in conjunction with plasma and/or urine cortisol. See Cushings syndrome , adrenocortical insufficiency .

Interpretation: 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).

Reference: Whitely RJ et al. In: Burtis CA and Ashwood ER eds. Tietz Textbook of Clinical Chemistry. 2nd ed. WB Saunders 1994.

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