Osteoporos Int 2021 Feb 9 DOI 10.1007/s00198-021-05871-0Thought to be the first study of its kind, Hamar, et al. have demonstrated the effect of one-year tofacitinib treatment on bone mineral density (BMD) in RA patients. While the association between RA and osteoporosis is well known, and evidence indicates that up to 70% of these patients have reduced BMD, little information is available on how the JAK inhibitor tofacitinib affects bone status, areal and volumetric BMD, and bone turnover markers. In this prospective study, 30 patients were assessed with the effects of one-year tofacitinib therapy on bone metabolism in RA. Randomised 1:1 to receive tofacitinib 5mg or 10mg BID, patients were assessed over a 12-month period. Using DXA, and peripheral QCT to determine areal and volumetric BMD, respectively, the study demonstrated that one-year tofacitinib treatment stabilised BMD in RA patients. Furthermore, assessment of bone biomarkers such as sclerostin, osteocalcin, osteoprotegerin, receptor activator of nuclear factor κB ligand, and 25-hydroxy-vitamin D3, indicated a positive balance of bone turnover resulting from tofacitinib therapy.In addition to bone biomarkers, univariable and multivariable analyses indicated that age, DAS28, and CRP also correlated with BMD.Although further studies are needed to evaluate the potential beneficial effects of JAK inhibitors on inflammatory bone loss, this is thought to be the first to show that tofacitinib therapy slows down bone loss in RA.