Unexpected low incidence of vertebral fractures in heart transplant recipients: analysis of bone turnover.

Heart transplantation (HTX) is associated with a reduction in bone mineral density (BMD). Different markers of bone metabolism have been used, and the applied immunosuppressive regimens have also changed over time. This study was performed to re-investigate bone metabolism in HTX recipients. Twenty-five HTX recipients were compared with 25 HTX candidates in respect of biochemical parameters of bone metabolism, BMD, and the frequency of fractures for 1 year. Osteopenia or osteoporosis was observed in approximately two-thirds of the HTX recipients. Nevertheless, only three (12%) HTX recipients developed a vertebral fracture within 1 year after transplantation; no peripheral fractures occurred. Compared with HTX candidates, HTX recipients had lower serum levels of osteocalcin, and higher serum levels of cross-linked-N-telopeptide of type I collagen (NTX). In HTX recipients, osteocalcin initially reached a nadir, increased during the first 3 months, and decreased thereafter. Bone-specific alkaline phosphatase initially increased and then decreased. Serum levels of NTX and parathyroid hormone remained high throughout the year. Despite a high bone turnover, an unexpectedly low rate of vertebral fractures was registered. Nevertheless, each fragility fracture is a serious complication and we need to take steps to prevent this complication.