Iodine and thyroid hormones

Czech version

Authors: R. Bílek; J. Čeřovská
Authors‘ workplace: Endokrinologický ústav, Praha, ředitel doc. MUDr. Vojtěch Hainer, CSc.
Published in: Vnitř Lék 2006; 52(10): 881-886
Category: Original Contributions

Overview

During the period 1995-2002, the urinary iodine concentration and serum thyroglobulin (TG, n = 3902), thyrotropin (TSH, n = 5162), free thyroxine (FT4, n = 5160), and free triiodothyronine (FT3, n = 4931) was determined in randomly selected population (n = 5263, 2276 male, 2987 female, with age varied from 6 to 98 years) of seven counties from Czech Republic. The measurement of iodine was based on alkaline ashing of urine specimens preceding Sandell-Kolthoff reaction. The thyroid hormones, TSH, and TG was determined in serum using immunoassays. The individuals were divided to the groups according their iodine deficiency, i.e. to the group with urinary iodine concentration < 50, 50-100, 100-200, and >200 µg I/L of urine. In these groups the mean and median of TG, TSH, FT4, and FT3 was calculated. The means and medians of TG and FT4 was increased with the decrease of urinary iodine, and TSH was decreased with the decrease of urinary iodine. The values of FT3 were relatively independent on changes in concentrations of iodine in urine. All the hormonal changes was fallen to the normal reference ranges. It is evident from our results that in the situation of iodine deficiency, when the concentration of TSH is decreased, the sensitivity of thyrocytes on TSH stimulation must be increased to active the increased concentrations of TG and FT4. TG was also the most appropriate indicator of iodine nutrition from all observed hormones.

Key words:
iodine - thyroglobulin - thyrotropin - thyroxine - triiodothyronine

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