Background : Numerous studies reported that thyrotoxicosis is associated with increased bone turnover and bone loss. However, studies of the effect of thyroxine theraphy on bone mineral density(BMD) have given conflicting results.
Method : To evaluate the influence of thyroid hormone therapy on BMD, we measured BMD of lumbar spine(L2-4), femoral neck, trochanter, and Ward’s triangle using dual energy X-ray absorptiometry (DEXA) in 44 women (13 premenpausal, 44.5+/-6.3 years; 31 postmenopausal, 57.2+/-5.9 years) who had been receiving the thyroxine therapy at least more than 1 year due to thyroid nodular disease and in 127 healthy control subjects without levothyroxine therapy(35 premenopausal, 44.4+/-5.3 years; 92postmenopausal, 57.2+/-7.4 years). Bone turnover was assessed by biochemical markers.
Result : Mean duration of thyroxine therapy was 27.3+/-13.9 months in premenopausal women, and 32.2+/-28.7 months in postmenopausal women, and the mean TSH values were not suppressed in both groups (0.8+/-0.7muIU/mL and 0.7+/-1.4muIU/mL, respectively). In the thyroxine treated pre-and postmenopausal groups. BMD was not different from
those of the controls is lumbar spine(L2-4), femoral neck, trochanter and Ward’s triangle. BMD at any site was not significantly correlated with duration of thyroxine therapy. Osteocalcin was increased in postmenopausal thyroxine-treated group than in control group, but there was no statistical significance (p=0.06). Total alkaline phosphatase was significantly elevated in postmenopausal thyroxine-treated group than in control group(p<0.05). There were signficant correlations between T3 concentration and osteocalcin (r=0.4627, p=0.013)or alkaline phosphatase (r=0.5712, p=0.01) in
postmenopausal thyroxine-treated group. And also these correlations were more markedly increased in postmenopausal group with TSH concentration lesser than 0.05 muIU/L(with osteocalcin, r=0.8363, p=0.005, with alkaline phosphatase, r=0.8447, p=0.002).
Conclusion : These results suggest that thyroxine therapy with a normal TSH does not have a significant effect on bone mineral density in pre- and postmenopausal women.
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