Hypercortisolism affects glomerular and tubular function in dogs.

Renal function was assessed in 25 dogs with Cushing's syndrome and in 12 healthy controls. Routine renal parameters and glomerular filtration rate (GFR) were measured and urinary biomarkers such as urinary albumin (uALB), urinary immunoglobulin G (uIgG), and urinary retinol-binding protein (uRBP) were assessed by ELISA. Urinary N-acetyl-β-D-glucosaminidase activity (uNAG) was determined colorimetrically. All urinary markers were indexed to urinary creatinine concentration (c). Plasma exo- (Cl(exo)) and endo-iohexol (Cl(endo)) clearance were used to measure GFR. Based on a Mann-Whitney U test, urea and Cl(exo) did not differ, sCr was significantly lower, and UPC, uALB/c, uIgG/c, uRBP/c, uNAG/c and Cl(endo) were higher in the dogs with Cushing's syndrome when compared with controls. The findings indicate that glomerular and tubular function are both altered in dogs with Cushing's syndrome. Further longitudinal studies will be required to elucidate the pathogenesis of the changes in GFR.