Vitamin D Repletion in Korean Postmenopausal Women with Osteoporosis

PURPOSE: Up to 71% of South Korean postmenopausal women have vitamin D deficiency {serum 25-hydroxyvitamin D [25(OH) D] level <50 nmol/L}. Data on vitamin D supplementation was collected during the screening phase of an efficacy/safety study of denosumab in Korean postmenopausal women with osteoporosis. This report describes the effect of vitamin D supplementation on repletion to 25(OH)D levels ≥50 nmol/L in Korean postmenopausal women with osteoporosis. MATERIALS AND METHODS: Vitamin D levels of Korean postmenopausal women (60–90 years old) were measured by extracting 25(OH)D(2) and 25(OH)D(3) from serum samples via protein precipitation and using liquid chromatography with tandem mass spectrometry detection. Calibration curves were constructed from the mass chromatograms to obtain total vitamin D levels. Subjects with serum 25(OH)D levels <50 nmol/L were supplemented with 1000 IU of vitamin D tablets during the 2.5-month-long screening period. Dose, frequency, and duration were determined by the investigator. If repletion was achieved (≥50 nmol/L) on retest, subjects were eligible to be rescreened for study entry. RESULTS: Of 371 subjects screened, 191 (52%) required vitamin D supplementation, and 88% (168 of 191) were successfully repleted. More than half of the subjects (58%) who were successfully repleted received doses of 2000 IU daily. The mean time to successful repletion was 31 days (standard deviation 8.4 days; range 11–48 days). CONCLUSION: Supplementation with daily median doses of 2000 IU vitamin D successfully repleted 88% of Korean postmenopausal women with osteoporosis within 48 days to a serum vitamin D level of 50 nmol/L.