GLOMERULAR HYPERFILTRATION IN YOUNG POLYNESIANS WITH TYPE-2 DIABETES

An increase in glomerular filtration rate (hyperfiltration) may be an important early event in the initiation of diabetic nephropathy but the prevalence of hyperfiltration appears to vary between different populations with type 2 diabetes. We have measured glomerular filtration rate using Cr-51 EDTA clearance in 15 young Polynesians (mean age 32 years), 1-30 months after the initial diagnosis of type 2 diabetes and 15 control Polynesian subjects of comparable age and sex distribution. The mean glomerular filtration rate in the diabetic subjects (216 ml/min) was 57% greater than that of the controls (137.5 ml/min, P < 0.0001). About one-third of their excess in glomerular filtration rate could be accounted for by the marked obesity of the diabetic subjects, but even after correcting for body size the diabetic subjects still had a significantly higher mean glomerular filtration rate than controls (165.6 vs. 119.6 ml/min per 1.73 m(2), P < 0.001); 73% of the diabetic subjects had hyperfiltration (> 140 ml/min per 1.73 m(2)). The diabetic subjects were normotensive but nonetheless had increased rates of albumin excretion (median 61 versus 9 mg/day, P < 0.001). We conclude that hyperfiltration is common in young Polynesians with recently diagnosed type 2 diabetes. Prospective studies are needed to determine whether this early abnormality of renal function heralds the later development of overt nephropathy.