Vitamin D metabolites and skeletal consequences in primary hyperparathyroidism

Primary hyperparathyroidism (PHPT) is associated with reduced bone mineral density (BMD) mainly at sites rich in cortical bone. However, successful parathyroidectomy causes an increase in BMD especially at sites rich in trabecular bone. Plasma 25-hydroxyvitamin D (25OHD) levels are typically reduced and plasma 1,25-dihydroxyvitamin D [1,25(OH)(2)D] slightly increased in PHPT. These variations in vitamin D metabolites may influence variations in BMD and fracture risk.

To investigate relations between preoperative vitamin D metabolites and skeletal consequences in patients with untreated PHPT and to appraise the influence of preoperative vitamin D metabolites on postoperative changes in BMD. Design Cross-sectional and cohort study.

Two hundred and forty-six consecutive Caucasian PHPT patients aged 19-91 years. (median 63, 87% females).

BMD was reduced at the femoral neck (P < 0.001) and forearm (P < 0.001), but normal at the lumbar spine (P = 0.11). Levels of biochemical bone markers were associated with high plasma PTH, high plasma 1,25(OH)(2)D and low plasma levels of 25OHD. Moreover, low plasma 25OHD was associated with low levels of BMD at the femoral neck (r(p) = 0.23), the forearm (r(p) = 0.19) and the whole body (r(p) = 0.30), whereas plasma 1,25(OH)(2)D was inversely associated with BMD at all regional sites and the whole body. Plasma PTH only showed an inverse association with BMD at the forearm (r(p) = -0.21). No association was observed between biochemical variables and prevalent spinal fractures, all peripheral fractures or osteoporotic peripheral fractures. The annual increase in spinal BMD after surgery was positively associated with preoperative plasma PTH (r(p) = 0.40), whereas the annual increase in whole body BMD was inversely associated with plasma 25OHD (r(p) = -0.32). No change in BMD at the femoral neck and forearm was observed 1 year after surgery.

Low vitamin D status and high plasma 1,25(OH)(2)D are associated with increased bone turnover and decreased BMD in patients with PHPT.