Parathyroid hormone reflects adiposity and cardiometabolic indices but not bone density in normal men

Abstract

Hyperparathyroidism may be associated with skeletal and cardiovascular abnormalities, but it is unclear whether these associations exist for high-normal levels of parathyroid hormone (PTH). We assessed relationships between PTH and anthropometric, skeletal and cardiometabolic indices in normal men. Body composition, blood pressure, biochemistry and bone mineral density (BMD) were evaluated in 151 healthy men. BMD was reassessed at 2 years, and coronary artery calcium (CAC) was measured at 3.5 years. Relationships between PTH and other baseline characteristics, CAC scores and change in BMD were evaluated. PTH correlated positively with baseline body mass index, fat mass, diastolic blood pressure, triglycerides, total and low-density lipoprotein (LDL) cholesterol, (r=0.19-0.25, P=0.02-0.002), and with category of CAC score. Relationships between PTH and cardiometabolic indices remained significant after adjustment for age, 25-hydroxyvitamin D and estimated glomerular filteration rate. Men in the top PTH tertile (⩾4.4 pmol l^-1, n=51) were more likely to have LDL cholesterol ⩾3.5 mmol l^-1, diastolic blood pressure ⩾85 mm Hg, and CAC score >0 than men in lower tertiles. PTH was not associated with history of fracture, baseline BMD, or change in BMD over 2 years. In summary, in this cohort of healthy men, PTH levels are linearly related to adiposity and to cardiometabolic indices, but not to BMD or bone loss. These findings suggest that adiposity should be considered as an independent cause of secondary hyperparathyroidism, and they may be relevant to patients with normocalcemic hyperparathyroidism, in whom high PTH levels may be a marker of adiposity and cardiometabolic risk rather than always indicating parathyroid autonomy.

Figure 1

Correlations between serum parathyroid hormone (PTH) and cardiometabolic risk factors. r, Pearson correlation coefficient; BMI, body mass index.

Figure 2

Relationship between serum parathyroid hormone (PTH) level and coronary artery calcium (CAC) score. CAC score categories are shown on the x-axis, where a score of 0 indicates low cardiovascular risk. PTH values are means and error bars represent 95% confidence intervals. P=0.0005 for linear trend (ANOVA, linear contrasts).

Figure 3

Proportion of men (n=151) with cardiometabolic risk factors, stratified by parathyroid hormone (PTH) level. *Denotes a significant difference between tertiles, P<0.05 (Chi squared). BMI, body mass index; CAC, coronary artery calcium; DBP, diastolic blood pressure; FBG, fasting blood glucose; HDL, high-density lipoprotein cholesterol; LDL, low-density lipoprotein cholesterol; SBP, systolic blood pressure.