Increased urinary excretion of transferrin in children with type 1 diabetes mellitus.

Urinary transferrin excretion was measured by radioimmunoassay in 74 children with Type 1 diabetes mellitus and in 40 normal children, and compared with urinary excretion of albumin, alpha-1-microglobulin, and N-acetyl-beta-D-glucosaminidase. Urinary transferrin excretion was significantly elevated in diabetic (median (range) 186 (18-1671) mg mol-creatinine-1) compared with normal (85 (27-668) mg mol-creatinine-1) children (p less than 0.001). Seventeen diabetic children had transferrin excretion above the 95th centile for normal children. In contrast there was no significant increase in urinary albumin excretion in the diabetic children although 8 had urinary albumin excretion which exceeded the 95th centile for normal children (6 of these 8 patients having coexistent urinary hyperexcretion of transferrin). Urinary transferrin excretion correlated significantly with urinary albumin excretion in both normal (rs = 0.62, p less than 0.001) and diabetic (rs = 0.61, p less than 0.001) children. The indices of proximal renal tubular function (urinary excretion of alpha-1-microglobulin and N-acetyl-beta-D-glucosaminidase) correlated significantly with transferrin excretion in both diabetic (rs = 0.43 and rs = 0.41, p less than 0.001) and normal (rs = 0.40, p less than 0.02 and rs = 0.53, p less than 0.001) children, but not with albumin excretion (rs = 0.20, p greater than 0.05 and rs = 0.22, p greater than 0.05). In addition urinary transferrin excretion significantly correlated with urinary glucose concentration (rs = 0.34, p less than 0.007) in Type 1 diabetic children. The discrepancy in urinary excretion of transferrin and albumin may reflect impaired proximal renal tubular reabsorption of transferrin and/or altered glomerular basement membrane selectivity for the two proteins.