Norm of ACTH Stimulation Test
17-Hydroxycorticosteroid (17-OHCS) levels increase by two to four times between the first and second 24-hour urine collection.
Usage of ACTH Stimulation Test
Definitive diagnosis of Addison's disease and adrenal adenoma.
Description of ACTH Stimulation Test
Adrenocorticotropic hormone (ACTH) is secreted by the pituitary gland and acts on the adrenal cortex to cause release of adrenal hormones. This test measures blood cortisol and urinary 17-OHCS levels before and after an infusion of ACTH. It is diagnostic of Addison's disease in a client with hypocortisolism when an infusion of ACTH fails to cause an increase in cortisol or 17-OHCS, urinary metabolites of plasma cortisol. A small response occurs in those with high mortality in the ICU and in older clients.
Professional Considerations of ACTH Stimulation Test
Consent form NOT required.
- To prevent hypersensitivity reactions when using biologic rather than synthetic ACTH, give 0.5 mg of dexamethasone orally before the test.
- Obtain a 3-L container with 10 mL of concentrated hydrochloric acid (HCl) preservative.
- Write starting time of collection on the laboratory requisition.
- The test can be performed at any time of the day.
- Discard the first morning-urine specimen.
- Save all urine voided for 24 hours in a refrigerated, clean, 3-L container to which 10 mL of concentrated HCl has been added. Document the quantity of urine output during the collection period. Include urine voided at the end of the 24-hour period.
- Begin a second 24-hour urine collection.
- During the second collection, infuse 24 units of ACTH in 500 mL of normal saline intravenously over 8 hours.
- Record the total 24-hour output on the laboratory requisition and send the entire specimen to the laboratory.
Client and Family Teaching
- Save all urine voided in the 24-hour period, and urinate before defecating to avoid loss of urine. If any urine is accidentally discarded, discard the entire specimen and restart the collection the next day.
Factors That Affect Results
- Maintenance steroids that must be given during the testing period should be in the form of small doses of dexamethasone to avoid false elevation of 17-OHCS in the urine.
- The test should be repeated in 24 hours if pituitary deficiency is suspected. Pituitary insufficiency would be evident by a gradual but small response to the ACTH stimulation test during the second test.
- The ACTH stimulation test is useful for identifying adrenal insufficiency; however, it is not sensitive or specific for clients suspected of having secondary adrenal insufficiency or those with recent pituitary injury.