1. The influence of family history of hypertension on the relationships between blood pressure, relative body weight, sodium/creatinine ratio of the 24 h urine, plasma renin activity and the plasma concentration of prolactin and parathormone were examined in 102 healthy male students.
2. Grouping together results from all students showed significant positive correlations between systolic blood pressure and prolactin, parathormone as well as relative body weight, between plasma renin activity and prolactin and a significant negative correlation between plasma renin activity and sodium/creatinine ratio of the 24 h urine.
3. By dividing the students into two groups according to their family history of hypertension we could demonstrate in those with family history of hypertension a highly significant positive correlation between mean blood pressure and sodium/creatinine ratio of the 24 h urine and an improvement of the correlations between systolic blood pressure and prolactin and between sodium/creatinine ratio of the 24 h urine and plasma renin activity. In students without family history of hypertension these relationships were no longer detectable. In the students without family history of hypertension the correlations between systolic blood pressure and relative body weight as well as between plasma renin activity and prolactin gained substantially in significance. In students with positive family history of hypertension these correlations could no longer be demonstrated. The correlations between systolic blood pressure and parathormone remained unaffected by family history of hypertension.
4. The results suggest that a genetic predisposition to essential hypertension is able to intensify the blood pressure effect of Na intake and of prolactin, which, besides its function as a sex hormone, is presumed additionally to be able to retain salt. However, the positive relationship between body weight and blood pressure, as well as between plasma renin activity and prolactin, the significance of which increases greatly in subjects without family history of hypertension, appears to be lost as the result of the increased sensitivity to salt in positive family history of hypertension.
