Endocrine Abstracts

Background: Thyroid-stimulating hormone (TSH) might influence bone mineral density (BMD) through its regulation of the thyroid hormones thyroxine (T4) and triiodthyronine (T3). Direct effect of TSH on bone turnover, mediated through its receptors on both osteoblast and osteoclast precursors, has been suggested. We wanted to explore the relationship between serum TSH, fT4 and BMD in women with different TSH levels after a long-term observation of thyroid function and bone status.

Methods: This study included 151 premenopausal women (age 36.4±6.8 years) and 153 postmenopaual women (age 60.9±7.7 years) with valid measurements of BMD at the hip and lumbar spine by dual energy X-ray absorptiometry (DEXA). Based on the TSH levels (ref. 0.32–5.0 mU/l), Premenopausal women were divided into two different groups: group 1 (n=101) with normal serum TSH (2.38±1.24 mU/l) and group 2 (n=50) with low TSH (<0.5 mU/l). Postmenopausal women were divided also into two groups: group 1 (n=79) with the upper normal TSH (2.5–4 mU/l) and group 2 (n=74) with lower normal TSH (0.5–2.5 mU/l) and we compared these groups each other.

Results: After multivariate adjustment, in premenopausal women, the group 1 with normal serum TSH, had significantly higher TSH (P<0.001), lower fT4 (P<0.001) and higher BMD at the lumbar spine and hip (P<0.01), as compared to group 2. In postmenopausal women, group 1 had significantly higher serum TSH (P<0.001), higher BMD at the lumbar spine and hip (P<0.05). No difference between these two groups has been found in the level of fT4.

Conclusions: Generally, we have demonstrated that lower serum TSH (In premenopausal women TSH<0.5 mU/l, and in postmenopausal women TSH<2.5 mU/l) was associated with significant decrease of BMD. Serum TSH below 2.5 mU/l was associated with higher BMD mainly in postmenopausal women. The results support clinical attention toward skeletal health in the patient with low TSH.