Effects of IGF-I on renal function in patients with chronic renal failure

Insulin-like growth factor I (IGF-I) has been shown to increase glomerular filtration rate and renal plasma flow in rats and humans with normal renal function. However, rats with reduced renal function are resistant to these effects. To determine whether IGF-I affects glomerular filtration rate and renal plasma flow in humans with reduced renal function, we administered recombinant human IGF-I (rhIGF-I) to patients with moderate chronic renal failure. Four patients whose baseline inulin clearances were 21.9, 23.2, 34.9, and 55.1 ml.min-1.1.73 m-2 were placed on a 1 g.kg-1.day-1 protein diet and studied over a 10-day period (0-10). On days 4-7, 100 micrograms/kg of rhIGF-I was subcutaneously administered twice daily to the patients. The effects of rhIGF-I on levels of circulating IGF-I, inulin clearance, p-aminohippurate (PAH) clearance, kidney volume, plasma glucose, plasma and urine calcium and phosphate, and urine sodium and protein were determined. Administration of rhIGF-I increased levels of circulating IGF-I, inulin clearances, PAH clearances, and kidney size in each of the four patients receiving the growth factor. IGF-I did not cause weight gain, natriuresis, proteinuria, or hypoglycemia. Plasma calcium and phosphate were not affected by rhIGF-I. However, the percent tubular reabsorption of filtered phosphate was increased. We conclude that administration of rhIGF-I can enhance glomerular filtration rate and renal plasma flow at least in some humans with moderately reduced renal function. The enhancement is associated with an increase in kidney volume.