[Increase of circulating levels of insulin and C-peptide: common factors in essential hypertension and overweight].
The aim of our study was to investigate the hypothesis that insulin resistance is involved in the pathogenesis of essential hypertension, and to explain whether hyperinsulinemia in this condition is the result of either pancreas overproduction or defective hepatic insulin clearance. In 14 lean normotensive, 17 overweight normotensive, 17 lean essential hypertensive, and 20 overweight essential hypertensive subjects, we measured, after overnight fasting, blood glucose, serum insulin, and serum C-peptide, and calculated the glucose/insulin and the insulin/C-peptide ratios, which can be commonly taken as indexes of peripheral sensitivity to insulin and hepatic insulin clearance, respectively. When compared to lean normotensives, overweight and/or hypertensive patients exhibited higher serum insulin and C-peptide concentrations, and a lower glucose/insulin ratio. No difference was found in the insulin/C-peptide ratio between normotensive and hypertensive subjects. Diastolic blood pressure was directly correlated with serum insulin (p less than 0.01) and C-peptide (p less than 0.01), and inversely correlated with the glucose/insulin ratio (p less than 0.02). We conclude that insulin resistance is present in both essential hypertensive and overweight subjects. Considering the normality of the insulin/C-peptide ratio when taken as the hepatic insulin clearance index, we believe that hyperinsulinemia is caused by a beta-cell hypersecretory response to the defective peripheral action of the hormone.