title: Levothyroxine dose and fracture risk according to the osteoporosis status in elderly women.
abstract: OBJECTIVE
  To evaluate the association between fracture risk and levothyroxine use in elderly women with hypothyroidism, according to previous osteoporosis history.
  
  
  METHODS
  We conducted a cohort study from the Korean Health Insurance Review and Assessment Service claims database from January 2005 to June 2006. The study population comprised women aged ≥65 years who had been diagnosed with hypothyroidism and prescribed levothyroxine monotherapy. We excluded patients who met any of the following criteria: previous fracture history, hyperthyroidism, thyroid cancer, or pituitary disorder; low levothyroxine adherence; or a follow-up period <90 days. We categorized the daily levothyroxine doses into 4 groups: ≤50 µg/d, 51 to 100 µg/d, 101 to 150 µg/d, and >150 µg/d. The hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated with the Cox proportional hazard model, and subgroup analyses were performed according to the osteoporosis history and osteoporosis-specific drug prescription status.
  
  
  RESULTS
  Among 11 155 cohort participants, 35.6% had previous histories of osteoporosis. The adjusted HR of fracture for the >150 µg/d group, compared with the 51 to 100 µg/d group, was 1.56 (95% CI, 1.03 to 2.37) in osteoporosis subgroup. In the highly probable osteoporosis subgroup, restricted to patients who were concurrently prescribed osteoporosis-specific drugs, the adjusted HR of fracture for the >150 µg/d group, compared with the 51 to 100 µg/d group, was 1.93 (95% CI, 1.14 to 3.26).
  
  
  CONCLUSIONS
  While further studies are needed, physicians should be concerned about potential levothyroxine overtreatment in elderly osteoporosis patients.
authors.affiliation: Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Young-Jin
authors.initials: YJ
authors.lastname: Ko
authors.affiliation: Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Ji Young
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Medical Research Collaborating Center, Seoul National University Hospital, Seoul, Korea.
authors.forename: Joongyub
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Family Medicine, Hallym University College of Medicine, Chuncheon, Korea.
authors.forename: Hong-Ji
authors.initials: HJ
authors.lastname: Song
authors.affiliation: Department of Family Medicine, Health Promotion Center, Seoul National University Bundang Hospital, Seongnam, Korea.
authors.forename: Ju-Young
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Medical Research Collaborating Center, Seoul National University Hospital, Seoul, Korea.
authors.forename: Nam-Kyong
authors.initials: NK
authors.lastname: Choi
authors.affiliation: Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Korea. ; Korea Institute of Drug Safety and Risk Management, Seoul, Korea.
authors.forename: Byung-Joo
authors.initials: BJ
authors.lastname: Park
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D016208:Databases, Factual; D005260:Female; D050723:Fractures, Bone / Q000517:prevention & control*; D006801:Humans; D007037:Hypothyroidism / Q000175:diagnosis / Q000188:drug therapy; D007345:Insurance Claim Review; D055118:Medication Adherence; D010024:Osteoporosis / Q000473:pathology*; D016016:Proportional Hazards Models; D018570:Risk Assessment; D013974:Thyroxine / Q000627:therapeutic use*; D013997:Time Factors
chemical_list: D013974:Thyroxine
keywords: Aged; Cohort studies; Fractures; Osteoporosis; Thyroxine