Serum parathyroid hormone as a predictor of increase in systolic blood pressure in men.

BACKGROUND In cross-sectional studies there appears to be a link between calcium metabolism and blood pressure, and most studies have found a positive association between serum parathyroid hormone (PTH) and hypertension. OBJECTIVE To determine the prognostic value of serum PTH regarding a future increase in blood pressure. DESIGN A prospective cohort study. SUBJECTS A total of 1784 individuals who had measurements of PTH in serum samples from both the fourth (1994) and fifth (2001) Tromsø studies, who did not use blood pressure medication during the observation period, and had serum calcium less than 2.61 mmol/l, were included. MAIN OUTCOME MEASURE Delta blood pressure (blood pressure from 2001 minus blood pressure from 1994). RESULTS The mean delta systolic blood pressure in the men and women during these 7 years was 5.8 and 8.1 mmHg, respectively. In a sex-specific linear regression model correcting for age, body mass index (BMI), and smoking status, serum PTH from 1994 was a significant predictor of delta systolic blood pressure in men (P < 0.01), but not in women. The difference in delta systolic blood pressure between those in the highest and those in the lowest PTH quartile was 3.5 mmHg. Similarly, delta serum PTH (serum PTH from 2001 minus serum PTH from 1994) was a significant predictor of delta systolic blood pressure in men (P < 0.05). CONCLUSIONS Although these findings do not prove a causal relationship between PTH and blood pressure, it adds to the growing number of indications that PTH is involved in the development of hypertension.