The Relationship of Subclinical Hypothyroidism with Bone Mineral Density and Biochemical Bone Markers in Postmenopausal Women

Background: It is well recognized that thyroid hormone stimulates bone turnover, increasing bone resorption, thus affecting bone mineral density, but few data are available on untreated subclinical hypothyroidism. The aim of this study was to examine whether bone mineral density is increased in postmenopausal subclinical hypothyroidism patients compared with postmenopausal normal thyroid function women, and to evaluate the relationship between thyroid hormones (TSH, FT4) and bone mineral density or various biochemical markers of bone metabolism. Methods: This was a cross sectional study of 132 postmenopausal women aged from 51 to 70 who undertook health screening program in Pundang CHA general hospital from 1996 to 2001. They were divided into two groups; subclinical hypothyroidism group (n=52) and normal thyroid function group (n=80) matched by age. Results: The total bone mineral density was significantly increased in the subclinical hypothyroid group than in the normal group (P<0.05). The serum osteocalcin was lower in the subclinical hypothyroidism group (P<0.05), but neither the alkaline phosphatase nor the deoxypyridinoline showed any significance. For all participants in this study, TSH, but not FT4, exhibited significant correlation with the total bone mineral density (r=0.188, P<0.05), and with the osteocalcin (r=-0.191, P<0.05). Multiple regression analysis identified the TSH as an independent predictor of the total bone mineral density (beta=0.0410; P<0.05). Conclusion: This study indicated that subclinical hypothyroidism is one of the factors which can elevate bone mineral density in postmenopausal women.