Actions of osteoporosis treatments on bone histomorphometric remodeling: a two-fold principal component analysis

This was the first study to apply principal component analysis method to bone histomorphometric parameters. The results corroborated teriparatide's distinct, yet different, mechanisms of action, which stimulate both bone formation and resorption. Introduction This study consolidated bone histomorphometric parameters and compared the effects of two osteoporosis treatments on bone remodeling by using a principal component analysis (PCA). Methods Included in this analysis were postmenopausal women with osteoporosis who were treated with either teriparatide or alendronate and who completed transiliac bone biopsy at either 6 or 18 months in the randomized, double-blind Forteo Alendronate Comparator Trial. Eighteen histomorphometric parameters were grouped into formation and resorption categories. The first principal component of each category was estimated through the PCA. The summation of principal formation component (PFC) and principal resorption component (PRC) was calculated to represent the overall level of bone turnover. The difference between PFC and PRC was computed to determine the balance between formation and resorption. Results The PFC was significantly higher in the teriparatide group than in the alendronate group (P<0.0001), while the PRC was numerically lower in the alendronate group (P=0.18). The mean difference between the PFC and PRC was positive in the teriparatide group and negative in the alendronate group. Conclusions Our approach of consolidating bone histomorphometric remodeling parameters corroborated the idea that the distinct, yet different, mechanisms of action of teriparatide treatment stimulate both bone formation and resorption, and alendronate treatment suppresses both bone formation and resorption.