title: Effects of teriparatide, alendronate, or both on bone turnover in osteoporotic men.
abstract: BACKGROUND
  We have previously demonstrated that alendronate reduces the ability of teriparatide to increase bone mineral density (BMD) in osteoporotic men. The underlying basis for this observation is poorly understood.
  
  
  OBJECTIVE
  The primary aim of this study was to determine whether teriparatide increases osteoblast activity when the ability of teriparatide to increase osteoclast activity is suppressed by alendronate.
  
  
  METHODS
  This was a nonblinded, randomized, controlled trial.
  
  
  METHODS
  The study was conducted at the General Clinical Research Center of a teaching hospital.
  
  
  METHODS
  We studied 63 men, age 46-85, with low spine and/or hip BMD.
  
  
  METHODS
  Subjects received alendronate 10 mg daily (group 1), teriparatide 37 microg sc daily (group 2), or both (group 3) for 30 months. Teriparatide was begun at month 6.
  
  
  METHODS
  The primary endpoint was the change in serum N-telopeptide, osteocalcin, and amino-terminal propeptide of type 1 procollagen.
  
  
  RESULTS
  In men receiving teriparatide monotherapy (group 2), levels of all bone turnover markers increased markedly during the first 6 months of teriparatide administration and then declined toward baseline during the next 18 months. In men who received combination therapy (group 3), bone turnover marker levels declined in the first 6 months (while receiving alendronate alone) and then returned to baseline levels (N-telopeptide) or above (osteocalcin and amino-terminal propeptide of type 1 procollagen) after teriparatide was added. Changes in each marker were significantly different between groups 1 and 2 (all P values < 0.001), groups 1 and 3 (all P values < 0.001), and groups 2 and 3 (all P values < 0.03).
  
  
  CONCLUSIONS
  As with BMD, alendronate impairs the action of teriparatide to increase bone turnover in men.
authors: Endocrine Unit, Bulfinch 327, Department of Medicine, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA. jfinkelstein@partners.org
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