The influence of PTH on volumetric bone density and geometry in obese subjects

Studies show that serum PTH levels are higher in obese than in nonobese adults. In this study we examined how PTH levels influences bone parameters and geometry, in obese women. Specifically we used peripheral quantitative computed tomography (pQCT) at the 14 and 38% site of the distal tibia to measure the bone parameters. We analyzed 22 women with a mean BMI of 42 ± 10 kg/m2. Serum PTH levels range was 17–141 pg/mL with a mean level of 71 ± 34 pg/mL. Linear regression analysis was used to assess the relationship with serum PTH. We found significant positive correlations between PTH and total, cortical and subcortical bone mineral content (BMC) and area, periosteal and endosteal circumferences, and the stress: strain index (SSI) at both the 14% and 38% sites (p ≤ 0.05), but not bone mineral density. Since weight was positively associated with serum PTH (p < 0.05) the regression analysis was also analyzed by adjusting for body weight, which attenuated the relationship, but most continued to show a trend (p < 0.10). In contrast to previous findings in normal weight postmenopausal women, our findings suggest that a high serum PTH in severe obesity has a weak, but positive effect on BMC, area, circumference and SSI. These findings however are limited by the number of subjects and require further study.