Effects of Oral Prednisone Administration on Serum Cystatin C in Dogs

Background Oral administration of glucocorticoid alters serum cystatin C ( sC ysC) concentration in humans. Objective To determine if oral administration of prednisone alters sC ysC in dogs without pre‐existing renal disease. Animals Forty six dogs were included: 10 dogs diagnosed with steroid responsive meningitis arteritis ( SRMA ; group A), 20 dogs diagnosed of pituitary‐dependent hyperadrenocorticism ( PDH ; group B), and 16 healthy control dogs (group C). Methods Retrospective observational study. SRMA diagnosed dogs were administered prednisone 4 mg/kg/24 h PO 7 days, reducing the dose to 2 mg/kg/24 h 7 days before medication withdrawal. In group A, sampling was performed at days 0, 7, 14 and a final control at day 21. Blood and urine samples were collected in the 3 groups, and in group A, sampling was performed at all time points (days 1, 7, 14, and 21). Results In group A, sC ysC was significantly higher at day 7 compared to the control group (0.4 ± 0.04 mg/L vs. 0.18 ± 0.03 mg/L mean ± SEM respectively P < 0.01); sC ysC values decreased to basal at day 14 when the dose was decreased and after 1 week of withdrawal of prednisone (0.27 ± 0.03 mg/L for group A at day 14 and 0.15 ± 0.02 mg/L at day 21; P > 0.05). Dogs with PDH included in group B did not have significant differences in sC ysC (0.22 ± 0.03 mg/L) compared to control ( P > 0.05). Conclusions and Clinical Importance Oral administration of prednisone unlike altered endogenous glucocorticoid production, increases sC ysC in dogs in a dose‐dependent fashion.