title: Bone mass, bone turnover and body composition in former hypothyroid patients receiving replacement therapy.
abstract: The aim of the present cross-sectional study was to disclose whether long-term thyroxine replacement therapy (TRT) in primary hypothyroidism causes osteopenia. We compared 36 adult biochemically and clinically euthyroid patients who had received TRT for more than 5 years (mean 13 years) for primary hypothyroidism with 80 sex- and age-matched normal controls. Height, body weight and lean body mass were similar, but the patients had 21% higher fat body mass (p = < 0.01) than their controls. Furthermore, compared to controls the patients had 29% higher serum thyroxine (T4) and 31% higher serum free T4 index (FT4I) levels (p < 0.001), whereas serum triiodothyronine (T3) and FT3I levels were both reduced by 7% (p < 0.05). In the patients, serum TSH was reduced significantly (p < 0.001). No significant differences were observed between patients and normals in regional or total bone mineral content or bone mineral density levels, apart from 20% higher lumbar bone mineral content among the premenopausal patients (p < 0.05). Surprisingly, the mean serum calcium level was slightly elevated (2.38 +/- 0.08 vs 2.33 +/- 0.07 mmol/l, p < 0.001), serum phosphate decreased (1.13 +/- 0.19 vs 1.23 +/- 0.16 mmol/l, p < 0.01) and 24-h renal calcium excretion was reduced by 19% (p < 0.05). No changes were observed in serum magnesium, intact parathyroid hormone or calcitriol. The biochemical markers of bone resorption (serum carboxyterminal telopeptide of type I collagen, renal excretion of hydroxyproline, pyridinoline and deoxypyridinoline) and formation (serum levels of carboxyterminal propeptide of type I procollagen, osteocalcin and total and bone alkaline phosphatase) were similar in the two groups. We conclude that long-term thyroxine replacement therapy in primary hypothyroidism does not exert a negative effect on bone mass or alter bone turnover.
authors.affiliation: Aarhus Bone and Mineral Research Group, University Department of Endocrinology and Metabolism, Denmark.
authors.forename: B L
authors.initials: BL
authors.lastname: Langdahl
authors.forename: A G
authors.initials: AG
authors.lastname: Loft
authors.forename: E F
authors.initials: EF
authors.lastname: Eriksen
authors.forename: L
authors.initials: L
authors.lastname: Mosekilde
authors.forename: P
authors.initials: P
authors.lastname: Charles
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers; D001823:Body Composition; D015519:Bone Density; D001842:Bone and Bones / Q000378:metabolism* / Q000473:pathology*; D002118:Calcium / Q000097:blood; D005260:Female; D006706:Homeostasis; D006801:Humans; D007037:Hypothyroidism / Q000188:drug therapy* / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D013961:Thyroid Gland / Q000503:physiopathology; D013974:Thyroxine / Q000627:therapeutic use*
chemical_list: D015415:Biomarkers; D013974:Thyroxine; D002118:Calcium