This study investigated whether or not vitamin D and calcium supplementation affected bone metabolism and bone mineral density (BMD) over a period of four years of denosumab therapy in patients with primary osteoporosis. Patients were divided into a denosumab monotherapy group (22 cases) or a denosumab plus vitamin D and calcium supplementation group (combination group, 21 cases). We measured serum bone alkaline phosphatase (BAP), tartrate-resistant acid phosphatase (TRACP)-5b, urinary N-terminal telopeptide of type-I collagen (NTX), and BMD of the lumbar 1-4 vertebrae (L-BMD) and bilateral hips (H-BMD) at baseline and at 12, 24, 36, and 48 months of treatment. There were no significant differences in patient background. Serum BAP, TRACP-5b, and urinary NTX were significantly and comparably inhibited in both groups from 12 to 48 months versus baseline values. L-BMD was significantly increased at every time point in both groups, while H-BMD was significantly increased at every time point in the combination group only. There were significant differences between the groups for L-BMD at 24, 36, and 48 months (P < 0.05) and for H-BMD at 12 months (P < 0.05). Compared with denosumab monotherapy, combination therapy of denosumab plus vitamin D and calcium significantly increased H-BMD at 12 months and L-BMD from 24 to 48 months. These findings indicate that continuous vitamin D and calcium supplementation is important, especially for 12 months to improve H-BMD and from 24 to 48 months to improve L-BMD.
Keywords: bone mineral density; bone turnover markers; denosumab; primary osteoporosis; vitamin D.