Endocrine Abstracts

Objective: Hyperthyroidism is accompanied by low bone mass. Because the reference range of TSH levels is defined statistically, some individuals with high-normal TSH levels (TSH <10 mU/l), may have mild hypothyroidism (subclinical hypothyroidism) and reduced bone mass. We therefore determined whether serum TSH levels correlate with bone mineral density (BMD) in persons with subclinical hypothyroidism.

Design: A cross-sectional study.

Participants: Thirty-two postmenopausal women, 18 with hypothyroidism (Hypo) and 14 with subclinical hypothyroidism (Sub Hypo).

Measurements: We measured BMD at the lumbar spine and femoral neck using dual energy X-ray absorptiometry, and serum TSH concentrations using immunoluminometry. Body mass index (BMI) was calculated from body weight and height.

Results: BMD at the lumbar spine (0.816±0.136 vs 0.881±0.106 g/cm², P=ns), and total left hip (0.715±0.133 vs 0.673±0.094 g/cm², P=ns) didnot differ between the groups. Patients with Hypo had higher level of TSH (7.95±1.51 vs 7.57±2.44, P=0.03) and it correlated negatively with BMD at the lumbar spine and total hip. In regression analysis, even after adjustment for age, years since menopause and BMI, subjects with Hypo (TSH≥10 mU/l) have shown significant association between TSH level and BMD at the lumbal spine (Adjusted R²=0.82, P=0.008) and femoral neck (Adjusted R²=0.78, P=0.004). In the group with Sub Hypo there were no significant association between TSH level and BMD.

Conclusion: These results suggest that high normal TSH level, maybe is not the cause of lower BMD in postmenopausal women, but low number of participants might be the reason of questionable conclusion.