The effect of timing of teriparatide treatment on the circadian rhythm of bone turnover in postmenopausal osteoporosis

BackgroundWe hypothesized that with the administration of teriparatide (TPTD) treatment at different times, we would be able to modify the physiological circadian rhythm of bone turnover.MethodsThe concentration of serum C-terminal telopeptide of collagen type I (βCTX), serum N-terminal propeptide of procollagen type I (P1NP), serum ionized calcium (iCa), and plasma PTH were measured every 3 h over a 24 h period in 14 postmenopausal osteoporotic women (aged 72.4±9.3 years) treated with 20 μg TPTD for long term, given at different times of the day. General linear model-repeated measurements (GLM RM) were performed to analyze the circadian rhythms as well as intergroup comparisons.ResultsGLM-RM for both related groups showed a significant influence of time of day on all measured variables except P1NP. The analysis for each group separately provided a powerful model for βCTX (P