Population based study on serum ionised calcium, serum parathyroid hormone, and blood pressure. The Tromsø study.

OBJECTIVE To study associations between serum ionised calcium, serum parathyroid hormone (PTH) and blood pressure. DESIGN A population based, cross-sectional study was used. METHODS Blood pressure, body mass index, serum ionised calcium and serum PTH were measured in 460 males and 486 females in the Tromso study in 1994/1995. None were on medication for hypertension. The data were analysed with a multiple linear regression model. RESULTS When looking at subjects with serum ionised calcium<1.39mmol/l, there was a significant negative association (P<0.01) between serum ionised calcium and PTH. There was no association between blood pressure and serum ionised calcium. In both sexes there was a significant positive association between age and serum PTH (P<0.01). For women, but not for men, there was a significant positive association between serum PTH and systolic and diastolic blood pressure (P<0.01). Within each age group there was a difference in both systolic and diastolic blood pressure of 3-10mmHg between the upper and lower serum PTH halves of the female population. Females with hypertension had significantly higher serum PTH levels than the normotensive females (P<0.01). CONCLUSION Serum PTH is strongly and positively associated with blood pressure in women.