title: Effects of levothyroxine on bone mineral density, muscle force, and bone turnover markers: a cohort study.
abstract: BACKGROUND
  Previous studies of the effects of levothyroxine (LT(4)) therapy on bone and bone metabolism have provided conflicting results.
  
  
  OBJECTIVE
  This study evaluated the potential effects and dose-response relationship of LT(4) therapy on bone mineral density (BMD) as well as bone and muscle strength.
  
  
  METHODS
  We conducted a prospective, nonrandomized, controlled cohort study with 1.1 ± 0.2-yr follow-up at an academic outpatient clinic in Germany.
  
  
  METHODS
  Ninety-seven men and premenopausal women were enrolled in the study after thyroidectomy and radioiodine remnant ablation for well-differentiated thyroid carcinoma (DTC) or strumectomy for nontoxic goiter. Patients were matched with 89 healthy controls.
  
  
  METHODS
  Twenty-eight men and 46 women on TSH-suppressive doses of LT(4) had DTC, and 23 women were on LT(4) replacement therapy for nontoxic goiter.
  
  
  METHODS
  This study assessed total and trabecular volumetric BMD (vBMD) as well as bone strength at the ultradistal radius, areal BMD at the lumbar spine and both hips, and the grip strength of the nondominant forearm. The dependent variables were annualized rates of change.
  
  
  RESULTS
  LT(4) therapy did not impair the areal BMD, bone strength, or grip strength of patients compared with controls. Women with DTC showed a significant loss of total vBMD, whereas men with DTC developed marginally less bone strength than women. Carboxy-terminal telopeptide indicated greater bone resorption in DTC patients compared with controls.
  
  
  CONCLUSIONS
  There was little evidence of adverse LT(4) effects on bone; however, premenopausal women with DTC might be at risk for reduced vBMD in their ultradistal radii.
authors.affiliation: University Hospital, Department of Nuclear Medicine, Oberdürrbacher Strasse 6, A4, 97080 Würzburg, Germany. Schneider_R1@klinik.uni-wuerzburg.de
authors.forename: Rita
authors.initials: R
authors.lastname: Schneider
authors.forename: Mara
authors.initials: M
authors.lastname: Schneider
authors.forename: Christoph
authors.initials: C
authors.lastname: Reiners
authors.forename: Peter
authors.initials: P
authors.lastname: Schneider
mesh_terms: D000328:Adult; D015519:Bone Density / Q000187:drug effects*; D002277:Carcinoma / Q000601:surgery; D015331:Cohort Studies; D005260:Female; D006042:Goiter / Q000601:surgery; D020249:Hormone Replacement Therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000187:drug effects*; D011446:Prospective Studies; D013964:Thyroid Neoplasms / Q000601:surgery; D013965:Thyroidectomy; D013974:Thyroxine / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: D013974:Thyroxine