Objective. To assess the structure of thyroid pathology in young elite athletes, depending on sex and type of sports. Materials and methods. The study included data from outpatient records of members of national sports teams, who underwent a comprehensive medical examination. Data of a random sample of 2307 outpatient records of young athletes in 26 sports were analyzed. Results. The prevalence of thyroid pathology in young elite athletes was 22.5%. Thyroid focal changes were detected in young athletes in 13.74% of cases; chronic autoimmune thyroiditis and subclinical hypothyroidism – in 4.2% and 3.85%, respectively. The frequency of single-node non-toxic goiter was 1.21%. Subclinical hypothyroidism was more often detected in combat and speed-power sports, while thyroid focal changes were more common in cyclic sports, team sports and complex-coordination sports. Nodular goiter was most often diagnosed in athletes engaged in cyclic sports. Conclusion. Young elite athletes are characterized by a high frequency of thyroid diseases. The features of the structure of thyroid pathology in certain sports were revealed. Further studies are needed to identify factors contributing to the development of thyroid diseases in young elite athletes. Key words: children, elite sports, endocrine pathology, thyroid diseases.

Results of hormonal tests of highly qualified athletes can differ significantly from the general population standards, which makes their interpretation difficult. The purpose of this research was to compare the prevalence of hormonal changes in adolescent athletes according to both the standard and the specialized reference intervals (RI). Materials and methods used: 2550 adolescent athletes, of which 1483 (58.1%) boys and 1067 (41.9%) girls from 28 kinds of sport aged 14 years to 17 years and 11 months old (ME: 16.1±1.1 y/o). All the young athletes have undergone the study of thyroid-stimulating hormone (TSH), free thyroxine (T4 test), cortisol, somatotropic hormone (STH) and total testosterone (chemiluminescent method with Lazurite automatic analyzer by Dynex Technologies Inc., USA) as part of an in-depth medical checkup of athletes in accordance with the Order of the Ministry of Healthcare of Russia No. 134n dated March 01, 2016, on the basis of the Federal Scientific and Practical Center for Children and Adolescents of the Federal Medical and Biological Agency of Russia (Moscow, Russia). The assessment of the hormonal profile was carried out according to both the standard RI and the specialized RI for young athletes. Results: when assessing the endocrine status of young athletes according to the standard RI, the frequency of hormonal changes was 30.6%, and 22.1% according to the specialized RI. When using specialized RI in male athletes, an increase in TSH and cortisol is recorded 2 times less often (p<0.001 for both parameters), an increase and decrease in total testosterone is determined in isolated cases, and hypersecretion of growth hormone is detected 6.5 times more often (p<0.0001). An increase in TSH when assessed using specialized RI in female athletes occurs 2 times less often (p<0.001). Hypersecretion of cortisol and growth hormone is recorded 20% (p=0.34) and 51% (p=0.02) less frequently, respectively. Conclusion: the use of the new RI does allow reducing of the frequency of detection of hormonal changes in adolescent athletes by 8.5% (p=0.03). The use of specialized RI of hormonal parameters in adolescent athletes to interpret TSH levels does not contradict with the modern clinical guidelines when deciding about the appointment of hormone replacement therapy for young athletes with subclinical hypothyroidism. The level of total testosterone, equal to 2.84 nmol/l, in young male athletes aged 16 to 17 y/o cannot be considered as a variant of the norm. The diagnostic value of determining growth hormone and cortisol in highly qualified athletes in adolescence is doubtful due to the high variability of the studied parameters and the complexity of interpreting the results obtained for practical use by a pediatric endocrinologist.