Insulin-like growth factor system and the kidney: physiology, pathophysiology, and therapeutic implications

The insulin-like growth factor (IGF) system, consisting of IGF-I and IGF-II, their binding proteins, and their receptors, is expressed in a spatial organization in the nephron, but circulating IGFs also affect the kidney. Renal and systemic IGF-I and the binding proteins are regulated by growth hormone and nutritional status. In the kidney, IGF-I dilates the resistance-regulating microvasculature, increases glomerular filtration rate, and promotes tubular phosphate and possibly sodium absorption. IGF-I contributes to compensatory renal growth in a variety of experimental models and may modestly contribute to progressive glomerular sclerosis. In chronic renal failure and the nephrotic syndrome, there are several abnormalities in the IGF system. In chronic renal failure, IGF-I increases renal function and may improve nutritional status due to its anabolic effects. IGF-I accelerates the recovery of renal function in animal models of acute renal failure, but results from clinical trials were less salutary. Several questions regarding the role of the IGF system in normal and abnormal renal biology and potential therapeutic applications in kidney diseases remain unanswered.