ACTHtestiin

ACTHtestiin, commonly referred to as the ACTH stimulation test, is a diagnostic procedure used to assess adrenal gland function by measuring the cortisol response after administration of adrenocorticotropic hormone (ACTH). It helps evaluate suspected adrenal insufficiency and differentiate between primary and secondary causes.

Procedure and variants

The standard test uses synthetic ACTH (cosyntropin) given by intramuscular or intravenous injection, typically 250 micrograms. Blood samples for serum cortisol are collected at baseline and at about 30 and 60 minutes after injection. Some protocols use only baseline and 60-minute measurements, and a low-dose variant (1 microgram cosyntropin) may be employed to increase sensitivity for secondary adrenal insufficiency.

Interpretation

A normal response generally requires a stimulated cortisol level above about 18 micrograms per deciliter (500 nanomoles per liter) at 30 or 60 minutes. A blunted or absent rise indicates adrenal insufficiency. In primary adrenal insufficiency (Addison disease), cortisol is low and ACTH is elevated. In secondary or tertiary forms (pituitary or hypothalamic), ACTH is low or inappropriately normal, and the cortisol response is often blunted.

Indications and limitations

Indications include evaluating symptoms of fatigue, hypotension, abnormal electrolytes, or suspected adrenal crisis, and prior to long-term glucocorticoid therapy where adrenal function is uncertain. Limitations include potential false results due to recent steroid use, acute illness, pregnancy, or certain medications that alter cortisol metabolism. The low-dose test may be more sensitive for secondary adrenal insufficiency in some cases.

Safety and accessibility

Cosyntropin administration is generally well tolerated. As with any blood test, transient dizziness or discomfort at the injection site may occur. The test results should be interpreted in the context of clinical findings and other endocrine studies.