Increased urinary excretion of the retinol-binding protein in insulin-dependent diabetes mellitus in the absence of microalbuminuria

Urinary excretion of the retinol-binding protein (RBP) was studied in 36 insulin-dependent diabetics with serum creatinine concentrations within the normal range and no microalbuminuria. The excretion was significantly (p < 0.05) higher in the diabetics as compared to a group of apparently healthy persons. The diabetes control indices HbA1 and serum fructosamine showed no correlation to the rate of urinary RBP excretion. The present data support the idea that tubular dysfunction may be an early symptom of diabetic nephropathy.