Tubular dysfunction and microalbuminuria in insulin dependent diabetes

Urinary growth hormone measurements as a marker of renal tubular function in diabetes mellitus

Urinary growth hormone (UGH) excretion was assessed in 44 adult subjects (10 control, 21 insulin dependent diabetics (Group I), 13 diabetics in poor glycaemic control (Group II)). UGH was markedly elevated in the diabetic population. The UGH excretion in (1) control subjects ranged from undetectable levels to 0.7 microU/h, mean 0.4, (2) Group I 73-422 microU/h, mean 250 and (3) Group II 10-5,283 microU/h, mean 705. There was a significant correlation between UGH excretion and albumin excretion rate (AER) (r = 0.38, P < 0.05) in the subjects studied although only 50% of patients had an AER of > 20 micrograms/min. A stronger correlation was observed between beta 2-microglobulin and UGH excretion (r = 0.7, P < 0.01). There was no significant change in the 6-h serum GH levels following treatment in the patients in Group II. However a 23-79% decline in UGH excretion was observed following improvement of glycaemic control, although UGH levels failed to revert to normal. We conclude that the major factor responsible for increased UGH excretion in DM appears to be reduced tubular reabsorption of the hormone. This test may therefore prove useful as an additional marker for screening for diabetic nephropathy and may help in the understanding of the contribution of renal tubular abnormalities to the nephropathic process.

Glomerular and tubular proteinuria in type 1 (insulin-dependent) diabetic patients with and without retinopathy

We compared the urinary excretion of albumin, transferrin, N-acetyl-beta-D-glucosaminidase and alpha-1-microglobulin in 78 Type 1 (insulin-dependent) diabetic patients: 39 with retinopathy and 39 without. The two groups were matched for age, sex and duration of diabetes. The patients with retinopathy had increased excretion (median and range) of albumin [1.7(0.3-399.1) versus 1.0(0.3-116.6) mg/mmol creatinine, P less than 0.05], transferrin [114.2 (4.1-37126.2) versus 33.4 (1.0-4176.7) micrograms/mmol creatinine, P less than 0.01] and N-acetyl-beta-D-glucosaminidase [23.8 (1.1-119.1) versus 15.0 (0.1-65.1) mumol/h/mmol creatinine, P less than 0.05] but not alpha-1-microglobulin. Transferrin excretion correlated with albumin excretion. The prevalence of increased transferrin excretion (transferrinuria) was greater than that of microalbuminuria in patients both with and without retinopathy (P less than 0.01 in both cases). Urinary transferrin seems likely to be predominantly of glomerular origin and merits prospective longitudinal evaluation as a potential index of the microangiopathic process.