To determine whether a decreased sensitivity to insulin is involved in the pathogenesis of essential hypertension, fasting blood glucose, serum insulin, serum C peptide, the glucose:insulin ratio and the insulin:C-peptide ratio were measured in 14 lean normotensives, 17 overweight normotensives, 17 lean hypertensives and 20 overweight hypertensives. Compared with the lean normotensives, the patients who were overweight, those with hypertension and those who were both overweight and hypertensive showed increased fasting serum insulin and C-peptide levels, and a lower glucose:insulin ratio. No significant difference between the normotensive and the hypertensive subjects was found in the insulin:C-peptide ratio. Diastolic blood pressure was directly correlated with serum insulin (P less than 0.01) and with C-peptide levels (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. Since the present study showed that hepatic insulin clearance was normal in hypertensives, the hyperinsulinaemia in essential hypertension appears to be due to beta-cell hypersecretion in response to a defective peripheral action of the hormone.
