Subclinical hyperthyroidism of variable etiology and its influence on bone in postmenopausal women.

Objective: To evaluate the effects of subclinical hyperthyroidism of variable etiology on bone mineral density (BMD) and bone metabolism in postmenopausal women.

Design: T he study included data of 88 postmenopausal women classified into four groups depending on the etiology of subclinical hyperthyroidism: (1) 20 with toxic multinodular goiter without history of clinical hyperthyroidism; (2) 25 on levothyroxine suppressive therapy after thyroidectomy due to differentiated thyroid cancer; (3) 21 with Graves' disease (GD) receiving antithyroid drugs; (4) 22 healthy women matched for age and duration of menopause. In all subjects biochemical markers of bone turnover and B MD were determined.

Results: Biochemical markers of bone turnover were significantly higher (p-value =0.001) in all patients with subclinical hyperthyroidism compared to the control group (group 4). T he women of group 1 had significantly lower B MD at all regions of the skeleton, whereas the women of group 3 had significantly lower B MD at Total Hip (p-value = 0.013) and Radius Total (p-value = 0.0003) compared to group 4. No significant differences in B MD between groups 2 and 4 were detected.

Conclusion: The etiology of subclinical hyperthyroidism influences B MD in postmenopausal women. Endogenous subclinical hyperthyroidism might be considered as an additional risk factor for osteoporosis in postmenopausal women, especially for cortical bone, whereas exogenous subclinical hyperthyroidism has no effect on BMD.