Adrenocorticotropic hormone (ACTH)

What it measures

ACTH is a pituitary hormone that stimulates cortisol release. Measured with cortisol, it separates primary from secondary adrenal disorders and pituitary from adrenal causes of Cushing syndrome.

Specimen and preparation

• Specimen: EDTA plasma
• Tube: Lavender top
• Preparation: Collect at 8–9 am into pre-chilled EDTA tubes, place on ice and centrifuge cold within 30 minutes; freeze plasma.

Reference range

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

• Addison disease (primary insufficiency)
• Cushing disease (pituitary)
• Ectopic ACTH-producing tumour
• Congenital adrenal hyperplasia
• Stress

Causes of low values

• Secondary adrenal insufficiency
• Adrenal Cushing syndrome (tumour)
• Long-term glucocorticoid therapy

Method

Chemiluminescent immunoassay

Good to know

ACTH degrades rapidly at room temperature, giving falsely low values.

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