Parathyroid hormone and the risk of incident hypertension.

OBJECTIVE: The presence of parathyroid hormone receptor mRNA in a wide variety of tissues, including the endothelium, suggests that parathyroid hormone has potentially important effects in addition to the maintenance of calcium and phosphate homeostasis. We conducted a prospective study to examine the association between plasma intact parathyroid hormone levels and the subsequent risk of developing hypertension.
METHODS: We measured intact parathyroid hormone in 481 men without hypertension from the Health Professionals Follow-up Study. During 10 years of follow-up, we observed 142 cases of incident hypertension. Cox proportional hazards regression was used to adjust for age, race, body mass index, alcohol use, smoking, physical activity, predicted plasma 25-hydroxyvitamin D level, and other factors.
RESULTS: Median baseline levels of intact parathyroid hormone were 40.1 pg/ml in individuals who developed hypertension and 36.3 pg/ml in those who did not (P = 0.01). After multivariate adjustment, the relative risk for incident hypertension in men in the highest quartile of parathyroid hormone (median 56.0 pg/ml) compared with the lowest quartile of parathyroid hormone (median 26.3 pg/ml) was 1.83 (95% confidence interval 1.10-3.03; P for trend = 0.01). Analyses restricted to men in the lowest 90th percentage of the parathyroid hormone distribution (< or =58 pg/ml) yielded similar results. Further adjustment for the intake of calcium and sodium, as well as for season and fasting status at time of blood draw, did not materially change the results.
CONCLUSION: Plasma levels of intact parathyroid hormone, even within ranges considered normal, are positively and independently associated with a higher risk of incident hypertension.