Statistical analysis of fat and muscle mass in osteoporosis in elderly population using total body DXA scans.

BACKGROUND: The magnitude of effects of lean mass and fat mass on bone health is controversial, and this study is a contribution to understand its effects on skeletal composition. AIM: We explored the relationship of body fat and muscle parameters with bone mineral density (BMD) and age and observed if it changed when matched with body mass index (BMI) of the same study subjects. METHODS: One-hundred sixty-four community dwelling, ambulatory elderly attending the osteoporosis services of a Dublin hospital was recruited. Out of these, 158 female patients had a total body DXA scan, and their body composition outcomes were included in this analysis. The relationship between body fat and muscle composition and BMD at all sites was determined and also matched by BMI. RESULTS: Total-Body BMD had a strong positive correlation with lean mass(r = 0.492, p 0.00) and fat mass(r = 0.414, p 0.00), though lean mass remained the strongest predictor of BMD at all sites. Increasing BMI categorically had a positive effect on both lean mass and fat mass. Increasing age was significantly associated with an increase in fat mass(r = 2.40, p 0.00) and a decrease in muscle mass(r = 0.478, p 0.01). CONCLUSION: Both lean mass and fat mass are significant predictors of BMD. To preserve BMD maintenance or increase of lean mass is more effective than fat mass. BMI correlates well with body composition; however, we recommend the use of direct measures of body fat and muscle to make this relation more interpretable. Total Body DXA is a readily available diagnostic tool which provides high-valued information about body composition.

Treatment of osteoporosis with recombinant parathyroid hormone, utilisation of total body DXA to observe treatment effects on total body composition and factors determining response to therapy.

PURPOSE: Recombinant parathyroid hormone (rPTH) increases bone mineral density (BMD). However, certain other potential effects of rPTH remain to be studied. The aim of this study is to identify whether bone turnover markers, relevant biochemical parameters or total body fat and muscle composition affect the response to rPTH and to establish if these parameters in particular change during treatment. METHODS: One hundred seventy-two participants were treated with rPTH, and 128 subjects who fully complied with the therapy and completed their investigations including biochemical bone markers and total body composition at baseline, 6 months and 1 year of the treatment were divided into responder and non-responder groups. A total body dual-energy X-ray absorptiometry (DXA) scanner was used to assess the body muscle, fat and bone composition. RESULTS: rPTH significantly increased BMD spine at 1 year (p = 0.000). Twenty-four-hour urinary calcium was significantly increased at 6 months in the responder group (p = 0.00). There was a trend to an increase in the fat and muscle mass (p = 0.52 and 0.45, respectively), and it was not negatively affected by rPTH. Bone turnover markers (P1NP and OC) did not show statistically significant difference over time between responders and non-responders (p = 0.74 and p = 0.19, respectively). CONCLUSIONS: Hypercalciuria which is a frequent feature in osteoporotic population may predict non-responders at 6 months of rPTH, and it may help to optimise individual patient's treatment. Unlike endogenous PTH in pathological conditions, rPTH is anabolic to bone and has no detrimental effects on the body fat and muscle composition.