Fat mass is an important predictor of parathyroid hormone levels in postmenopausal women

Previously, we reported that people with elevated parathyroid hormone (PTH) levels due to primary hyperparathyroidism have increased body weight compared to eucalcemic controls. We sought to determine whether the same relationship between PTH and body weight exists in eucalcemic healthy postmenopausal women, and to investigate the relationships between components of body weight, PTH, vitamin D metabolites, and metabolic indices. We performed a cross-sectional analysis of 116 healthy community-dwelling postmenopausal women. Pearson correlation analysis was used to test for univariate linear relationships between variables, and stepwise multiple regression analysis to assess for multivariate relationships. We found that PTH was significantly positively correlated with body weight, regional and total fat mass, and percent body fat, and negatively correlated with activity levels, 25 hydroxyvitamin D (250HD), dietary calcium intake, and serum phosphate. On multivariate analysis, PTH was positively related to percent body fat (P = 0.020; partial r(2) = 0.10) and negatively related to dietary calcium intake (P = 0.041; partial r(2) = 0.03) and serum phosphate (P = 0.026; partial r(2) = 0.04). Adjusting for vitamin D insufficiency or 250HD levels did not affect the relationship between PTH and fat mass. For 250HD, there were significant positive correlations with lumbar spine BMD and serum albumin, and significant negative correlations with PTH, total fat mass, trunk fat, and pelvic fat. On multivariate analysis, 250HD was positively related to serum albumin (P = 0.008; partial r(2) = 0.07) and negatively related to pelvic fat mass (P = 0.014; partial r(2) = 0.05). Adjusting for PTH levels did not change the relationship between 250HD and pelvic fat mass. We conclude that fat mass is a significant independent determinant of serum PTH levels, and that this relationship is independent of the inverse relationship between 250HD and fat mass. This association between fat mass and PTH might contribute to the association between primary hyperparathyroidism and increased body weight. (c) 2005 Elsevier Inc. All rights reserved.