Division of Endocrinology, Department of Medicine, Faculty of Medicine, Srinakharinwirot University, Maha Chakri Sirinthorn Medical Center, Nakhon-Nayok 26120, Thailand.
Background: Calcium supplement for postmenopausal osteopenic women can significantly reduce bone loss and the risk of fractures. However, the optimal time for calcium supplementation remains controversial.
Objective: The aim of the present study was to compare the effect of twice daily post meals and bedtime calcium supplementation for a two week periods, on C-terminal telopeptide crosslinks and PTH levels in postmenopausal osteopenic women.
Design: A randomized double blind placebo-control, crossover design, was carried out on 3 consecutive periods 3 of a 2-week treatment regimen. In the first period, all the subjects randomly received either two calcium carbonate tablets (Chalk Cap all subjects randomly received either two calcium 334 mg per tab) or placebo at bedtime with one tablet of calcium tablet or placebo after breakfast and dinner for two weeks. In the second period, subjects received only placebo tablets after the meals and at bedtime for 2 weeks. In the third period subjects received either calcium carbonate or placebo for another two weeks. The C-terminal telopeptide crosslinks were measured at 8.00 am and serum PTH were sampled at 8 time points (12.00 am, 2.00 am, 4.00 am, 6.00 am, 8.00 am, 9.00 am, 5.00 pm, and 7.00 pm respectively by the end of each study at the first and third period.
Results: The present study showed thirty-six postmenopausal subjects (mean age 63.9 + 3.66 years) participated in the present study. The mean T-score BMD of the spine and hip were -2.96 + 0.87 and -2.96 + 0.77 gm/cm2. C-terminal telopeptide crosslinks levels of the bedtime supplementation were significantly lower than the post meal supplementation (0.228 + 0.002 ng/ml vs 0.313 + 0.003 ng/ml, p < 0.001). The mean night time serum PTH level during the bedtime was significantly lower than the post meal period. (25.17 + 2.31 pg/ml vs 31.930 + 2.677 pg/ml, p < 0.001). No differences in the post meal PTH level between two periods were observed
Conclusion: The bedtime calcium supplementation appeared to reduce the bone resorption marker and night time serum PTH levels greater than the post meal calcium supplementation in this short term period study. However, long term comparison may be needed.
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