Circulating PTH, Vitamin D and IGF-I levels in relation to bone mineral density in elderly women

Age and reduced bone mineral density (BMD) represent major risk factors for vertebral fracture risk, especially in pos-tmenopausal women, and measurement of BMD is currently considered of value in estimating bone mineralization. BMD correlates with demographics and anthropometric parameters, as well as with several markers of bone metabolism and calcium-regulating hormones, such as leptin, osteoprotegerin, parathyroid hormone (PTH), vitamin D, insulin-like growth factor-I (IGF-I) and sex steroid hormones. The aim of this study was to evaluate the relationship between PTH, 25(OH) vitamin D [25(OH)D], IGF-I and BMD in a selected group of elderly women. Thirty-one post-menopausal women over the age of 65, who were not estrogen, vitamin D or bisphosphonate users and did not have a history of fracture, bone disease or malignancy, were prospectively enrolled in the study. All the patients underwent lumbar spine dual-energy x-ray absorptiometry (DXA) and serum calcium, creatinine, PTH, 25(OH)D and IGF-I measurements. As expected, a weakly-inverse correlation between age and 25(OH)D (R=-0.50, p=0.020), and between BMD and PTH (R=-0.48, p=0.027) was found. There was a strong relationship between IGF-I and BMD (R=0.64, p=0.0016), and between age and IGF-I (R=-0.70, p<0.001), while IGF-I did not correlate with 25(OH)D (R=-0.16, p=0.48) or BMI (R=-0.089, p=0.70). In conclusion, in this selected group of elderly women, we found a strong relationship of increased bone resorption, expressed as BMD, to calcium-regulating hormones PTH and IGF-I, while 25(OH)D and BMI seem to be independent of bone mineralization status.