HYPERINSULINEMIA, FAMILY HISTORY OF HYPERTENSION, AND ESSENTIAL-HYPERTENSION

The aim of this study was the evaluation of the relationships among hy perinsulinemia, a family history of hypertension, and essential hypert ension. Insulin and C-peptide responses to an oral glucose load were s tudied in 175 lean normotensives (N) and untreated hypertensives (H) w ith (F+) and without (F-) a family history of hypertension: 30 NF-, 30 NF+, 45 HF-, and 70 HF+. The groups were comparable for age, sex, bod y mass index, and blood pressure, The following parameters were evalua ted: plasma glucose (G), serum insulin (I), and C-peptide (Cp) before and 30, 60, 90, and 120 min after the glucose load, fasting glucose/in sulin ratio (ISI), fasting insulin/C-peptide ratio (I/Cp), and 24-h am bulatory blood pressure monitoring. Plasma glucose was measured, fasti ng and during the test, and it and I/Cp were similar in the four group s, Serum insulin and Cp, both fasting and stimulated, were significant ly higher and ISI lower in normotensives and hypertensives with hypert ensive parents. Grouping the subjects first on the basis of blood pres sure and then on the basis of family history, no differences were foun d between normotensives and hypertensives, whereas I and Cp, fasting a nd stimulated, were significantly higher and ISI lower in subjects wit h positive as compared to negative family history. The closest correla tions between insulin and ambulatory blood pressure were found in norm otensives with hypertensive parents; in hypertensives with hypertensiv e parents we only found a direct correlation between fasting Cp and no cturnal blood pressure fall; in hypertensives with normotensive parent s insulin inversely correlated with nocturnal blood pressure fall. Ins ulin resistance seems to have a familial basis, independently of the p resence of hypertension. Instead of showing a causal relationship betw een insulin resistance and hypertension, our results indicate that the two are partly independent components of a common familial pattern.