Eldecalcitol increases bone mass in patients with Turner syndrome who have insufficient bone mass acquisition after estrogen replacement therapy.

Most patients with Turner syndrome (TS) exhibit amenorrhea due to premature ovarian failure. Therefore, estrogen replacement therapy (ERT) is required; however, even after undergoing ERT, it is not rare for bone mass acquisition to be insufficient. This study was conducted in two stages, involving a cross-sectional and a prospective interventional study. We recruited 52 TS patients undergoing ERT due to amenorrhea (categorized into low (LB group; n = 23), and normal (NB group; n = 29) bone mass groups) and 7 TS patients who maintained ovarian function (spontaneous menstrual cycle group (MC group)) as controls. We compared bone associated markers between the three groups (LB, NB, and MC). Furthermore, the LB group had concomitant treatment with eldecalcitol (ELD) and ERT for 12 months. The bone mineral density (BMD) of the lumber spine (L2-4) and the bone metabolism markers were then compared before and after the treatment. The bone metabolism markers were significantly higher in the LB group than the NB and MC groups. Furthermore, with the concomitant use of ELD and ERT in the LB group, BMD increased significantly (pre-treatment 0.710 ± 0.056 g/cm2 vs. 0.736 ± 0.062 g/cm2 after 12 months; p < 0.001). TS patients with insufficient bone mass acquisition even after ERT were characterized by a higher turnover in bone metabolism. Therefore, the concomitant use of ELD was considered an effective adjuvant therapy for increasing bone mass.