PPIB and osteoporosis: Compared with TAM-treated patients, AI-treated patients had low BMD and T values, indicating high proportions of bone loss and osteoporosis, and low levels of bone formation markers such as OC, procollagen type I N-propeptide, and total 25-hydroxyvitamin D in bone metabolism indexes in AI-treated patients, along with low levels of the bone resorption indicator β-collagen specific sequence (β-CTX).