Biochemical markers of bone turnover in patients with thyroid dysfunctions and in euthyroid controls: a cross-sectional study.

Hyperthyroidism is associated with reduced bone mineral density. Conflicting data exist regarding the effects of thyroxine therapy on bone metabolism. The aim of the present study was to assess changes in markers of bone turnover in thyroid dysfunction. A total of 28 patients with overt hyperthyroidism, eight patients with suppressed TSH levels (thyroid hormones within the euthyroid range, no T4 therapy), 25 euthyroid and four hypothyroid patients were included in the present study. Hyperthyroidism resulted in increased bone metabolism, as reflected by increased bone resorption and bone formation parameters. No significant differences in mean levels between patients with TSH supression and those with euthyroidism could be observed; however, a higher frequency of elevated urinary PYD- and DPD excretion rates were noted in patients with TSH suppression. Regression analysis revealed highly significant correlations between bone resorption markers and thyroid parameters, suggesting, that even a mild thyroid hormone excess may lead to an increase in bone resorption. In subjects with suppressed TSH levels and peripheral thyroid hormone levels within the euthyroid range, elevated bone resorption markers point to subclinical hyperthyroidism, if other reasons for an increase in bone turnover rates can be excluded.