title: The effect of timing of teriparatide treatment on the circadian rhythm of bone turnover in postmenopausal osteoporosis.
abstract: BACKGROUND
  We 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.
  
  
  METHODS
  The 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.
  
  
  RESULTS
  GLM-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<0.001, η(2)=0.496), serum iCa (P<0.001, η(2)=0.423), plasma PTH (P<0.001, η(2)=0.283), and serum PINP (P<0.001, η(2)=0.248). While the evening TPTD treatment showed a marked circadian rhythm for serum βCTX, the morning TPTD treatment rather suggested circasemidian rhythm. The P1NP rhythm followed a much smaller amplitude of the rhythm than βCTX. Changes in serum iCa were positively related to changes in serum βCTX (P<0.001) and negatively related to changes in PTH (P<0.001).
  
  
  CONCLUSIONS
  Timing of TPTD administration may significantly change the 24 h variation in bone turnover markers as well as calcium-parathyroid axis in postmenopausal osteoporotic women.
authors.affiliation: Department of Internal Medicine III-Department of Endocrinology and Metabolism, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, U Nemocnice 1, Cz-128 08 Prague, Czech Republic.
authors.forename: Maria
authors.initials: M
authors.lastname: Luchavova
authors.forename: Vit
authors.initials: V
authors.lastname: Zikan
authors.forename: Dana
authors.initials: D
authors.lastname: Michalska
authors.forename: Ivan
authors.initials: I
authors.lastname: Raska
authors.forename: Ales A
authors.initials: AA
authors.lastname: Kubena
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Stepan
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density / Q000187:drug effects; D050071:Bone Density Conservation Agents / Q000627:therapeutic use*; D002940:Circadian Rhythm / Q000187:drug effects*; D005260:Female; D006801:Humans; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000188:drug therapy* / Q000503:physiopathology; D019379:Teriparatide / Q000627:therapeutic use*
chemical_list: D050071:Bone Density Conservation Agents; D019379:Teriparatide