Low-Dose Dexamethasone Suppression Test-min

Low-Dose Dexamethasone Suppression

Diagnostic testing enables our team to pinpoint the underlying cause of your pet’s symptoms, diagnosing their condition(s). We want our pet parents to be involved in the decision-making process, and we thoroughly discuss the diagnostic testing we recommend for your pet and their diagnostic test results. Personalizing your pet’s diagnostic plan ensures we avoid unnecessary tests and procedures while leading us to a more personalized and effective treatment plan.

Diagnostic Overview 

Low-Dose Dexamethasone Suppression Test

A low-dose dexamethasone suppression (LDDS) test is a diagnostic tool used to measure the response in cortisol production from the adrenal glands in dogs and cats after administering a synthetic cortisone-type hormone called dexamethasone. 

This test is usually recommended when a Pet Health veterinarian wants to determine if your pet has Cushing’s disease, and it is the preferred screening test for most situations. During the test, a baseline cortisol sample is taken, and then a small amount of dexamethasone is administered intravenously. Two additional blood samples are taken at 4 and 8 hours to monitor the pet’s cortisol levels in response to the dexamethasone. In a normal pet, the pituitary gland should decrease its secretion of ACTH, resulting in a specific decrease in the cortisol level after 8 hours. With Cushing’s disease, there is a smaller-than-normal decrease in response to the presence of dexamethasone. 

This test is noninvasive and sensitive, and it can differentiate PDH from adrenal tumors in 50% of cases, which can avoid additional diagnostics and testing. The main disadvantage is that the test takes 8 hours to perform and can have false positives if a pet is systemically ill or takes external steroids. The sensitivity of this test is high (90-95%) for PDH, but it has a lower specificity (40-50%), meaning more false positives are likely. If a pet is systemically ill or taking external steroids, the LDDS test should be delayed, or ACTH stimulation testing should be done.