Abnormalities of renal function in essential hypertension with increased circulating levels of insulin-like growth factor I.

An increase in glomerular filtration rate and in tubular Na+ reabsorption from the parenteral administration of insulin-like growth factor I (IGF-I) have been reported in human subjects. To evaluate whether glomerular hyperfiltration and Na+ hyper-reabsorption present in some essential hypertensives are associated to an excess of IGF-I, the plasma levels of this factor and several parameters of renal function were studied in 30 non-treated essential hypertensives and in 30 normotensive controls. IGF-I levels were higher in hypertensive as compared to controls. With the 95% (upper) limit of the normotensive population as a cut-off point, a subgroup of six hypertensives had an abnormally high IGF-I level. Mean blood pressure was slightly lower in these six patients (112 +/- 7 mmHg) than in the remaining patients (120 +/- 2 mmHg). As compared to normotensives and hypertensives with normal IGF-I levels, patients with increased IGF-I levels were characterized by lower (P < 0.01) fractional Na+ excretion and higher (P < 0.05) creatinine clearance. The analysis of the relation of plasma renin activity and the concurrent daily rate of Na+ excretion showed that patients with increased IGF-I were low-renin hypertensives and patients with normal IGF-I were normal-renin hypertensives. These results indicate that an association exists between exaggerated circulating levels of IGF-I and abnormalities of renal function present in some patients with essential hypertension. It is suggested that IGF-I can play a role in low-renin essential hypertension.