Insulin-like growth factor-1 and glomerular filtration rate in hypertensive patients.

OBJECTIVE: Essential hypertension is a clinical condition associated with insulin resistance and progressive impairment of renal function that increases cardiovascular events. Insulin-like growth factor (IGF)-1, which is inversely related to insulin levels, increases renal blood flow and glomerular filtration rate (GFR). The aim of the present study was to investigate the relationship between circulating IGF-1 levels and GFR in a group of never treated hypertensive patients.
METHODS: The study population consisted of 537 outpatients presenting at Catanzaro University Hospital. To participate in this study, patients have to had a systolic clinic blood pressure (BP) of more than 140 and less than 180 mmHg or a diastolic BP of more than 90 and less than 100 mmHg or both on at least two separate visits. Blood samples were at least obtained after 8-10 h in fasting conditions. The GFR was estimated by the modification of diet in renal disease equation. Serum creatinine was measured in the laboratory by an automated technique. Insulin sensitivity was estimated by using the homeostasis model assessment index calculated from the fasting glucose and insulin concentrations.
RESULTS: Both fasting insulin and homeostasis model assessment significantly (P < 0.0001) show an inverse relationship with GFR decline, whereas IGF-1 presents a significant and direct relationship with it. As expected, IGF-1 and fasting insulin resulted in an inverse relationship between them (r = -0.318; P < 0.0001). The strongest predictor of GFR resulted IGF-1, accounting for a 9.8% of its variation; the addition of fasting insulin and systolic BP accounts for another 3.7% of the variation.
CONCLUSION: We demonstrate a significant relationship between IGF-1 and GFR in a large sample of never treated hypertensive patients, probably as consequence of insulin resistance/hyperinsulinemia, which is a very frequent condition in high BP.