Abstract
The structure of endocrine morbidity is characterized by a significant spread of thyroid pathology. The insufficient efficacy of inorganic iodine drugs poses the problem of search for new means for iodine deficiency treatment and prevention. Given the progressive aging of the population in economically developed countries, the purpose of the study was to clarify the effect of organic iodine on the features of absorption and elimination of radioactive iodine from the thyroid glands of variously aged rats in the conditions of iodine deficiency in the diet. The study was performed on nonlinear white male rats in two series of studies that were kept on iodine-deficient isocaloric starch-casein diet for 60 days: the first series included two groups of old rats weighing 0.400-0.450 kg, the second series – two groups of sexually immature rats weighing 0.060-0.090 kg. There were 5 rats in each group. In animals of the experimental groups in each series, 10% of casein in the diet was replaced with organic iodine, which came with iodine-protein preparation from the red Black Sea algae Phyllophora nervosa. The functional state of the thyroid gland was studied using the Sodium Iodide Na 131 I Injection drug. The dosimetry was performed using the STS-6 Geiger-Muller Detector. Radioindication of the thyroid gland was carried out after subcutaneous administration of 0.1 ml of 131I solution at the following time intervals: 0.5, 1, 2, 4, 6, 8, 10, 12, 24, 48, 72, and 96 hours after administration of 131I. The study results were presented as a percentage of the radioiodine dose administered, adjusted for natural radioactivity background and the radioactive decay of the drug. It was found that in the iodine deficiency conditions, the thyroid glands of old rats have higher rates of radioiodine absorption and a lower rate of its excretion than the glands of immature rats, which indicates their lower iodine reserve and greater liability to iodine deficiency pathology. Intake of organic iodine regardless of the rats’ age is accompanied by a decrease in radioiodine accumulation and acceleration of its excretion from the thyroid gland, which indicates a decrease in functional stress, but the glands of older rats absorb more iodine and excrete it more slowly, indicating less effective correction of iodine deficiency with age. Reduced functional activity of the thyroid glands in old rats can be used as a sensitive changes marker for the in-depth study of thyrotropic and thyroid disrupting effects.
Highlights
In the general system of control and regulation, which acts in the body with the direct participation of the endocrine system, one of the leading places belongs to the thyroid gland (TG) [18]
Based on the notion that the hypothalamic-pituitarythyroid complex is most sensitive to various impacts in sensitive periods of its development, the study of the impact of various substances on the functional state of the thyroid gland is usually performed on young laboratory animals [12]
The findings indicate that the thyroid glands of older animals have a smaller iodine reserve, as a result of which they are more susceptible to goitrogenic effects of iodine deficiency
Summary
In the general system of control and regulation, which acts in the body with the direct participation of the endocrine system, one of the leading places belongs to the thyroid gland (TG) [18]. The territory of Ukraine is characterized by a mosaic combination of biogeochemical areas with reduced iodine content in the environment and areas with anthropogenic and industrial contamination of the environment with heavy metal ions, substances with thyroid disrupting, and radioactive properties. All these factors can affect various parts of the hypothalamic-pituitary-thyroid axis, which can disrupt the synthesis, secretion, and transport of thyroid hormones (TH), distort their local effects on target cells, cause functional and organic changes in the gland with subsequent disorders of the whole body. Objective age-related changes in thyroid functional activity [20] and the progressive aging of the population in the vast majority of
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