Moreover, we did not test for bone turnover biomarkers (BTMs) such as procollagen type I N-propeptide (PNP1) and carboxy-terminal cross-linked telopeptide of type 1 collagen (CTX-1), which some prospective studies have suggested may be helpful in estimating fracture risk, an implicit goal of our research.36 BTMs have also been studied extensively in the context of HIV infection and ART use to better understand the mechanisms of bone loss in individuals living with HIV.37-39. Here, PTPN13 is linked to HIV infectious disease.