title: Thyroxine suppressive therapy decreases bone mineral density in post-menopausal women.
abstract: OBJECTIVE
  Hyperthyroidism is associated with increased bone turnover and decreased bone mass. This study aimed to evaluate the bone mineral density (BMD) of post-menopausal women on long-term thyroxine suppressive therapy.
  
  
  METHODS
  An age and sex-matched cross-sectional study.
  
  
  METHODS
  Thirty-four post-menopausal women with carcinoma of thyroid, post total thyroidectomy and 131I ablation, on L-T4 for 12.2 +/- 6.6 years (mean +/- SD). Controls were 34 age-matched healthy Southern Chinese women.
  
  
  METHODS
  Total body and regional BMDs were determined by dual-energy X-ray absorptiometry. Bone turnover was assessed by biochemical markers.
  
  
  RESULTS
  In the thyroxine treated group, total body mineral content was significantly lower than the controls (1652 +/- 356 vs 1994 +/- 270 g mean +/- SD, P < 0.005). They also had lower BMDs in the lumbar spine, femoral neck, trochanter and Ward's triangle (0.75 +/- 0.15 vs 0.92 +/- 0.16 g/cm2, P < 0.005; 0.62 +/- 0.12 vs 0.70 +/- 0.12 g/cm2, P < 0.01; 0.55 +/- 0.14 vs 0.63 +/- 0.15 g/cm2, P < 0.001; 0.55 +/- 0.14 vs 0.63 +/- 0.14 g/cm2, P < 0.005 respectively.) The thyroxine treated group also had higher serum alkaline phosphatase and osteocalcin levels as well as urinary hydroxyproline excretion, suggesting that they had high turnover bone loss. However, the Z-scores of the various regional BMDs were correlated only with the serum osteocalcin level and showed no correlation with the serum thyroxine level or with the dosage or duration of thyroxine treatment.
  
  
  CONCLUSIONS
  Long-term thyroxine suppressive therapy was associated with bone loss and preventive therapy may be indicated in these post-menopausal women at risk of osteoporosis.
authors.affiliation: Department of Medicine, Biochemistry, University of Hong Kong.
authors.forename: A W
authors.initials: AW
authors.lastname: Kung
authors.forename: T
authors.initials: T
authors.lastname: Lorentz
authors.forename: S C
authors.initials: SC
authors.lastname: Tam
mesh_terms: D015502:Absorptiometry, Photon; D015519:Bone Density / Q000187:drug effects*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008875:Middle Aged; D015675:Osteocalcin / Q000097:blood; D017698:Postmenopause / Q000097:blood; D011184:Postoperative Period; D013960:Thyroid Function Tests; D013964:Thyroid Neoplasms / Q000097:blood / Q000601:surgery; D013965:Thyroidectomy; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000009:adverse effects* / Q000097:blood / Q000627:therapeutic use
chemical_list: D007457:Iodine Radioisotopes; D015675:Osteocalcin; D013972:Thyrotropin; D013974:Thyroxine