Increased serum osteopontin is a risk factor for osteoporosis in menopausal women

Osteopontin (OPN)-deficient mice are resistant to ovariectomy-induced osteoporosis. Therefore, we hypothesized that women with OPN overexpression may show less resistance to postmenopausal osteoporosis. In this study, we first demonstrated that serum OPN levels could be used as a biomarker for the early diagnosis of osteoporosis in postmenopausal women. Animal studies indicate that OPN-deficient mice are resistant to ovariectomy-induced osteoporosis. From 2004 to 2006, 124 women over the age of 45 were enrolled in a menopausal group, while another 95 women, from 25 to 45 years of age with regular menstruation, were enrolled into a childbearing age group. The serum concentrations of OPN were calculated using the enzyme-link immunosorbent assay method, and bone mineral densities were determined with dual energy X-ray absorptiometry. Serum OPN levels had a significant positive correlation with age (menopausal group, p < 0.0001) and a negative correlation with body weight, height, hip bone mineral density, and T-scores in the menopausal group. In contrast, there was a positive correlation with the E2 concentration and height, but there was no significant association with the above variables in the childbearing age group. Additionally, high serum OPN levels (> 14.7 ng/ml) was a significant risk factor causing menopausal osteoporosis (odds ratio = 2.96, 95% confidence interval, 1.055-8.345). Serum OPN levels could be used as a biomarker for the early diagnosis of osteoporosis in postmenopausal women.