Objectives: We wished to determine whether women with multinodular goitre and spontaneous subclinical hyperthyroidism have decreased bone density.
Design and subjects: Bone density was measured at the distal and proximal forearm. Data were expressed as Z-scores relative to the mean values out of 125 control subjects matched for age and menopause. The Z-scores of 23 women with subclinical hyperthyroid goitre (TSH < 0.1 mU/l and normal values for FT4 and total T3) and of 54 women with euthyroid goitre were compared.
Measurements: Bone density was measured by single photon absorptiometry. TSH was measured by IRMA, FT4 by RIA.
Results: Relative to the euthyroid goitre subjects the mean +/- SEM Z-scores of both the distal and proximal forearm density were lower (-0.69 +/- 0.17 vs -0.1 +/- 0.18, P < 0.05 and -0.5 +/- 0.18 vs 0.07 +/- 0.18, P < 0.05, respectively). Median (range) FT4 in the subclinical hyperthyroid goitre subjects was significantly higher than euthyroid goitre subjects (15.6 (11-23.2) pmol/l vs 11.9 (8.3-18.3) pmol/l, P < 0.001) although still within the normal range. FT4 correlated inversely with Z-scores of both distal and proximal forearm bone density in the subjects with subclinical hyperthyroidism (r = -0.42, P < 0.05 and r = -0.43, P < 0.05, respectively), but not in the euthyroid goitre subjects.
Conclusion: These findings indicate that women with untreated multinodular goitre and subclinical hyperthyroidism have reduced bone density in the forearm.