ACP5 and osteoporosis: Presently, BTMs that are widely used in clinical diagnosis of osteoporosis include bone formation markers: osteocalcin (OC), N-terminal propeptide of Type I procollagen (P1NP), bone-specific alkaline phosphatase (b-ALP), and other markers; bone resorption markers: C-terminal telopeptide of Type I collagen (CTX-I), amino-terminal cross-linking telopeptide of Type I collagen (NTX-1), deoxypyridinoline (DPD) and tartrate-resistant acid phosphatase 5b (TRAcP5b), and other markers [99–102].