Test Background ACTH is a 39 amino acid peptide hormone which is secreted by the pituitary gland to regulate production of steroid hormones by the adrenal cortex. It is the principal modulator of cortisol. As the effective level of cortisol rises, release of ACTH is inhibited directly at a pituitary level. Plasma ACTH levels are useful in the differential diagnosis of pituitary Cushing’s disease, Addison’s disease, autonomous ACTH-producing pituitary tumours and ectopic sources of ACTH secretion.
Clinical Indications Establishment of the aetiology of Cushing's syndrome and assessment of treatment efficacy in Cushing’s patients Differentiation of primary from secondary causes of adrenal insufficiency Diagnosis of ectopic ACTH secretion, eg. small cell carcinoma of the lung Localisation of excess ACTH production
Reference Range 9am: 0-30 ng/L Midnight: 0-10 ng/L
Sample Required EDTA (lavender top) on ice rush to laboratory
Sample Collection Collect into tube on ice, separate in a chilled centrifuge and freeze immediately.
Sample Volume 0.5 mL
Transport/Storage Send to lab frozen.
Turnaround Time 1 week
Notes Grossly haemolysed samples are unsuitable for this assay.