Urine excretion of insulin and growth hormone in subjects with renal failure.

Abstract

ABSTRACT Fifty g oral glucose tolerance tests were performed on 25 subjects with chronic renal failure, 8 with the nephrotic syndrome and 6 recovering from acute renal failure. Urine was collected during a basal overnight period and during the glucose tolerance test and immunoreactive growth hormone (GH) and insulin were determined in serum and urine. Sixteen acromegalic subjects with normal renal function were also studied since unlike insulin, GH could not be measured in unconcentrated urine in healthy control subjects. Insulin and GH clearances were markedly elevated in chronic renal failure and in patients recovering from acute renal failure, but raised in 3 subjects only with the nephrotic syndrome. In spite of this marked elevation of clearance in chronic renal failure patients, in any one subject insulin and GH clearance remained relatively constant. There was a correlation between insulin clearance and GH clearance during the glucose tolerance test, indicating that the patients with the higher insulin clearances also had the raised GH clearances. Since a common path of degradation of GH and insulin has not been demonstrated the results suggest that changes in tubular cell transport are responsible. GH clearance in uncomplicated acromegalic subjects was about 1/50 of the insulin clearance in healthy controls. This ratio fell to unity in patients with very severe chronic renal failure with creatinine clearances of 2 ml/min. In 2 patients with creatinine clearances of less than 2 ml/min the insulin and GH clearance approached the creatinine clearance, suggesting that GH and insulin in the glomerular filtrate were not reabsorbed by the proximal tubule. Since normal renal clearances of insulin and GH are so low and clearance changes so dramatically in renal failure, measurement of these hormones may provide a useful and simple assessment of proximal tubular function.