Multivariate regression analysis of the risk of decreased bone density at the FN has 2 factors: age (OR = 1.117), PTH (OR = 1.001); at the LS, there are 3 factors: gender (OR = 4.572), PTH (OR = 4.078), age (OR = 1.045); at the total H, there are 2 factors: PTH (OR = 3.683), age (OR = 1.117).