Background: Primary hyperparathyroidism (PHPT) is associated with hypertension, coronary atherosclerosis and other cardiovascular diseases. We aimed to evaluate serum parathyroid hormone (PTH) levels as an independent risk factor for coronary heart disease (CHD) in subjects with serum calcium within the reference range.
Design: Population-based cross-sectional study.
Methods: The Tromsø Study was attended by 27159 subjects aged 25-79 years. Serum PTH was measured in 3570 subjects. They all completed a questionnaire on medical history, including questions on angina pectoris and myocardial infarction along with a food-frequency questionnaire. A total of 1459 men and 1753 women with serum calcium 2.20-2.60 mmol/l, serum creatinine<121 micromol/l and who did not use diuretics were included in the present study. Linear regression was used to reveal associations between PTH, age, body mass index, serum calcium, calcium intake, cholesterol, blood pressure, glycosylated haemoglobin (HbA1c) and smoking status. A logistic regression model was used to find the independent predictors of CHD.
Results: When stratified for age the rate of CHD was higher in the subjects with serum PTH > 6.8 pmol/l than in those with normal or low serum PTH levels [relative risk 1.67, 95% confidence interval (CI) 1.26-2.23 in men and 1.78, 95% CI 1.22-2.57 in women]. The highest PTH quartile (> 3.50 pmol/l in men and > 3.30 pmol/l in women) predicted CHD, with odds ratios of 1.70 (95% CI 1.08-2.70) for men and 1.73 (95% CI 1.04-2.88) for women, versus the lowest PTH quartile (< 1.90 pmol/l for men and <1.80 pmol/l for women).
Conclusions: Serum PTH predicts CHD in subjects with calcium levels within the reference range. This may indicate a role for PTH in the development of CHD.