Diagnosis of Cushing's syndrome in a guinea pig (Cavia porcellus) applying the modified version of the low-dose dexamethasone-suppression test used in canines

The low dose dexamethasone stimulation test (LDDST) is routinely used in canine medicine but in the few cases in guinea pigs diagnosed with hypercortisolism, the adrenocorticotropic hormone (ACTH) stimulation test was used. The objective of the authors was to conduct a pilot study and find out if the standard test used in dogs can be used in this species. A 4-year-old intact female hairless guinea pig showed bilaterally enlarged adrenal glands and high cortisol levels. Urine was collected and, after initial saliva sample collection, 0.01 mg*kg −1 dexamethasone was administered. Saliva was collected with a 1 mL syringe to determine cortisol levels upon 2, 4 and 8 h after dexamethasone application. The urine cortisol:creatinine ratio was above 465.4*10 −6 . Before applying dexamethasone, the cortisol level was 171 nmol*L −1 . 2 h after initial application, it was 79 nmol*L −1 , at 4 h it was 70 nmol*L −1 , and at 8 h it rose to 1,280 nmol*L −1 . The LDDST used in canine medicine to diagnose hypercortisolism can be adapted to guinea pigs and yields results to diagnose Cushing's syndrome in this species. As dexamethasone is more accessible, cheaper and more sensitive than the ACTH stimulation test, it should be a preferred choice from all aspects.