BROMINE AND THYROID-HORMONE ACTIVITY

Aims-To examine the possible consequences of high plasma concentration s of bromine on thyroid hormone. Methods-Bromine was measured by induc tively coupled plasma mass spectrometry in the plasma of 799 patients consulting for thyroid disorders. Because the mean (SD) bromine concen tration in the plasma of healthy subjects is 4 (1) mg/l, concentration s above 6 mg/l were regarded as outside the normal range. Bromine, fre e thyroxine (FT4), and thyroid stimulating hormone (TSH) values were c ompared. Results-The percentage of patients with normal, low, and high FT4 and TSH plasma activities, measured separately, did not differ be tween patients with low and high bromine concentrations. The percentag e of patients with high TSH but normal FT4 values was significantly hi gher in the group with bromine values of more than 6 mg/l than in the group with bromine concentrations below this (p < 0.02). Conclusion-An increase in plasma bromine could potentiate an increase in plasma TSH concentration, probably as a consequence of a minor inhibitory effect on thyroid activity.