Dynamics of the body weight changes induced by iodine of organic and inorganic chemical nature in the conditions of subclinical hyperthyroidism

Abstract

Aim. To study features of the effect of iodine of different chemical nature on the body weight in subclinical hyperthyroidism. Materials and Methods. The study was performed on 90 white outbred male rats with body weight of 140-160 g, kept on a standard starch-casein diet, with potassium iodide being eliminated from the saline mixture. The model condition of subclinical hyperthyroidism was induced by thyreoidin added to the food mixture at a histologically tested dose of 15 mg/100 g body weight. The source of inorganic iodine was a potassium iodide solution; the source of organic iodine was iodine-protein drug of the red Black Sea algae Phyllophora crispa. Iodinated supplements were added to the food mixture in amounts that ensured supply of the following histologically verified doses of iodine: small (21 μg/kg body weight), optimal (50 μg/kg body weight), and significant (100 μg/kg body weight). Body weight was determined by weighing animals with the medical scales once a week. The total of 5 tests has been performed. Results and Discussion. Consumption of iodine-containing agents by the rats caused a significant increase in the indices of body weight, the parameters of which depended on the chemical nature and dose of iodine consumed. Under the influence of organic iodine, the final growth rates were 55% when receiving a small dose, 84% - an optimal dose, and 98% - a significant dose. When consuming inorganic iodine, the highest rates (58 and 51%) were observed under the influence of small and moderate doses; the least (43%) - when consuming a significant dose. Analysis of weekly body weight gain showed that regardless of the chemical nature of the consumed iodine, the most intensive growth occurred during the first week of the study. The gain indices of the following (second, third, and fourth) weeks were determined both by the dose of iodine consumed and by its chemical nature: intake of inorganic iodine at the doses of 50 and 100 μg/kg body weight was accompanied by moderate (16-14%) weight gains during the third and the fourth weeks; organic iodine consumption caused the weight gains during the third week (22%). Conclusion. Under the conditions of thyreoidin-induced subclinical hyperthyroidism, addition of iodine compounds to the iodine deficient diet is accompanied by an increase in the body weight of rats, which is logical to be considered a consequence of iodine-induced blockage of hormone-producing processes in the thyroid gland. The phenomenon of the most intense body weight growth during the first week can be considered an adaptive reaction to the activating (“stress inducing”) iodine action under the conditions of increased functional activity of the thyroid gland. Lower body mass indices, which were established in the consumption of inorganic iodine, indicate its milder effect, which gives grounds to consider the influence of inorganic iodine under hyperthyroidism more physiological than the effect of organic iodine.

Keywords

• thyroid gland, subclinical hyperthyroidism, body weight, organic iodine, inorganic iodine