Relationship between bone mineral density, PTH, vitamin D and insulin-like growth factor-1 in postmenopausal women with secondary hyperparathyroidism

Secondary hyperparathyroidism (SHPT) represents a risk factor for adverse skeletal-related events, especially in elderly women with reduced BMD. Elevated circulating PTH levels leads to both anabolic and catabolic effects on bone cells. There is evidence that part of the effects of PTH are mediated by local production of IGF-1, which physiologically regulates skeletal growth and development. The purpose of this study was to evaluate the relationship between calcium-regulating hormones PTH, vitamin D and IGF-1 and BMD in postmenopausal women with SHPT. Patients & Methods: The data relating to a group of 19 elderly (median 68 years, range 65–70 years) osteoporotic (T-score<2.5) women with mild SHPT, mainly related to the use of loop diuretics, were retrospectively collected and analyzed. All patients underwent lumbar spine (LS) DXA and LS-BMD measurement, together with serum PTH, 25(OH) vitamin D, and IGF-1 assay. Results: There was an inverse weak relationship between age and PTH (R=0.39, p=0.09) or BMD (R=0.41, p=0.08), but no correlation with 25(OH) vitamin D (R=0.23, p=0.34) or IGF-1 (R=0.15, p=0.54). A significant correlation was observed between IGF-1 and BMD (R=0.68, p=0.001) or PTH (R=0.47, p=0.04) and, as expected, a strong inverse correlation between PTH and BMD (R=0.63, p=0.003). No relationship between 25(OH) vitamin D and PTH (R=0.12, p=0.62) or BMD (R=0.28, p=0.24) was found. Conclusion: In elderly women with SHPT, IGF-1 and PTH have synergistic actions on bone, and both are significantly related to BMD, while 25(OH)D seems to be independent from bone mineralization measured al LS site.