ACTH stimulation test

The ACTH test (also called the cosyntropin, tetracosactide, or Synacthen test) is a medical test usually ordered and interpreted by endocrinologists to assess the functioning of the adrenal glands stress response by measuring the adrenal response to adrenocorticotropic hormone (ACTH; corticotropin) or another corticotropic agent such as tetracosactide (cosyntropin, tetracosactrin; Synacthen) or alsactide (Synchrodyn). ACTH is a hormone produced in the anterior pituitary gland that stimulates the adrenal glands to release cortisol, dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEA-S), and aldosterone. The ACTH test (also called the cosyntropin, tetracosactide, or Synacthen test) is a medical test usually ordered and interpreted by endocrinologists to assess the functioning of the adrenal glands stress response by measuring the adrenal response to adrenocorticotropic hormone (ACTH; corticotropin) or another corticotropic agent such as tetracosactide (cosyntropin, tetracosactrin; Synacthen) or alsactide (Synchrodyn). ACTH is a hormone produced in the anterior pituitary gland that stimulates the adrenal glands to release cortisol, dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEA-S), and aldosterone. During the test, a small amount of synthetic ACTH is injected, and the amount of cortisol (and sometimes aldosterone) that the adrenals produce in response is measured. This test may cause mild side effects in some individuals. This test is used to diagnose or exclude primary and secondary adrenal insufficiency, Addison's disease, and related conditions. In addition to quantifying adrenal insufficiency, the test can distinguish whether the cause is adrenal (low cortisol and aldosterone production) or pituitary (low ACTH production). The Insulin tolerance test is recognized as the gold standard assay of adrenal insufficiency, but due to the cumbersome requirement for a two-hour test and the risks of seizures or myocardial infarction, the ACTH stimulation test is commonly used as an easier, safer, though not as accurate, alternative. The test is extremely sensitive (97% at 95% specificity) to primary adrenal insufficiency, but less so to secondary adrenal insufficiency (57-61% at 95% specificity); while secondary adrenal insufficiency may thus be dismissed by some interpreters on the basis of the test, additional testing may be called for if probability of secondary adrenal insufficiency is particularly high. Adrenal insufficiency is a potentially life-threatening condition. Treatment should be initiated as soon as the diagnosis is confirmed, or sooner if the patient presents in apparent adrenal crisis. This test can be given as a low-dose short test, a conventional-dose short test, or as a prolonged-stimulation test. In the low-dose short test, 1 µg of an ACTH drug is injected into the patient. In the conventional-dose short test, 250 µg of drug are injected. Both of these short tests last for about an hour and provide the same information. Studies have shown the cortisol response of the adrenals is the same for the low-dose and conventional-dose tests. The prolonged-stimulation test, which is also called a long conventional-dose test, can last up to 48 hours. This form of the test can differentiate between primary, secondary, and tertiary adrenal insufficiency. This form of the test is rarely performed because earlier testing of cortisol and ACTH levels in association with the short test may provide all the necessary information. The test should not be given if on glucocorticoids or adrenal extract supplement, as these will affect test results. Stress and recently administered radioisotope scans can artificially increase levels and may invalidate test results. Spironolactone, contraceptives, licorice, estrogen, androgen (including DHEA) and progesterone therapy may also affect both aldosterone and cortisol stimulation test results. To stimulate aldosterone, consumption of salt should be reduced to a minimum and foods high in sodium avoided for 24 hours prior to testing. Women should ideally undergo testing during the first week of their menstrual cycle as aldosterone (and occasionally cortisol) may be falsely elevated in the luteal cycle secondary to progesterone inhibition, leading to a compensatory rise in aldosterone levels. Traditionally, cortisol and ACTH levels (separate lavender top tube) are drawn at baseline (time = 0). Next, synthetic ACTH or another corticotropic agent is injected IM or IV, depending on the agent. Approximately 20 mL of heparinized venous blood is collected at 30 and 60 minutes after the synthetic ACTH injection to measure cortisol levels.