Dr.Med., Professor E.A. Turova¹
PhD E.A. Tenyaev¹
PhD A.V. Golovach¹
PhD I.N. Artikulova^1
1Moscow Scientific and Practical Center for Medical Rehabilitation, Restorative and Sports Medicine, Moscow Department of Health

Keywords: athletes, endocrine disorders, thyroid diseases, iodine deficiency, hypothyroidism, autoimmune thyroiditis, thyroid nodule.

Background. The study of the prevalence and structure of endocrine diseases in athletes is a topical problem of restorative and sports medicine. High physical loads and emotional stress inherent in modern sports place special requirements on the energy supply system of the athlete’s body [2]. During the athletes' adaptation to physical loads, including those of submaximal power, the hypothalamic-pituitary-adrenal and sympathetic-adrenal systems - the hormonal link of control of the adaptation process, are activated; however, the role of other hormonal systems in the adaptation processes is poorly studied. This is particularly true for the thyroid gland, which vital role in the regulation of energy metabolism is beyond doubt [3]. Changes in the hormonal status of young athletes reflect their level of stress after training loads. However, impaired hormonal balance affects the functioning of different systems of the body and can cause failure of adaptation and development of endocrine disorders. Nowadays, there is a lack of convincing evidence and reliable data, both from the statistical and clinical analyses of thyroid diseases among athletes.

Objective of the study was to assess the structure and prevalence of diseases of the endocrine system in athletes based on the peculiarities of age- and sport-specific endocrine disorders.

Methods and structure of the study. The study involved an analysis of the medical records of the athletes who had undergone an in-depth medical examination on the basis of Branch 1 of the State Autonomous Healthcare Institution of Moscow Centre for Research and Practice in Medical Rehabilitation, Restorative and Sports Medicine of Moscow Healthcare Department. We analyzed the data from a random sample of medical records of 604 athletes engaged in 48 sports, who had undergone the in-depth medical examination in 2016-2018. We considered the data of sports history, anthropometric measurements, thyroid, abdominal, and pelvic ultrasonography, results of the clinical and biochemical surveys of athletes, hormonal blood spectrum rates (TSH, free T4, prolactin, testosterone, cortisol, TPO antibodies), data of the instrumental survey (ECG, impedance monitoring, echocardiography, cycle ergometer test, spirometry).

Results and conclusions. By sex, a larger share (65%) was represented by males (394 males) and a smaller (35%) - by females (210 females): at a ratio of 1.9:1.0. The age of the examined athletes ranged from 12 to 38 years and the mean age was 18.07 years. Their sports experience ranged from 2 to 22 years, with an average of 9.4 years. In the vast majority of cases (134 subjects or 38% of all pathologies detected), the athletes were diagnosed with thyroid diseases. Of all the examined athletes, 22% were found to have different thyroid diseases. According to the data of the Ministry of Health of the Russian Federation, the incidence of thyroid diseases among the entire population in 2017 amounted to 346.4 per 100,000, i.e. 0.3%. [5], and the incidence of thyroid diseases among adolescents aged 15-17 years - to 113.4 per 100,000, i.e. 0.1%.

Thus, the prevalence of thyroid diseases in Russia is significantly higher than the national average, including the adolescent population. We assume that this is primarily due to the thorough examination of athletes aimed to reveal diseases at the latent stage, when there are no complaints or obvious clinical manifestations. However, high physical loads in modern sports, which place special demands on the hormonal component of regulation of adaptation, cannot be excluded either. There is some evidence that not only physical but also mental workloads can lead to a breakdown in adaptation and contribute to the development of a number of diseases, including those of the endocrine system [1]. The majority of the examined athletes, who were predominantly 15-17 years of age, schoolchildren preparing for admission to institutes and colleges, were affected by a combination of both physical and mental workloads, which could exacerbate the imbalance in the adaptation mechanisms. With regard to the structure of the thyroid disease (Fig. 1), sub-clinical hypothyroidism was the most common (47 athletes or 7.8% of the total sample). Iodine deficiency conditions came second (41 athletes or 6.8% of the total sample), being characterized by cystic degeneration of thyroid tissue (colloid cyst).

Fig. 1. Structure of thyroid disease in athletes

Therefore, every 7th athlete was found to have signs of iodine deficiency or hypothyroidism. Autoimmune thyroiditis came third: it was found in 26 athletes (4.3% of the total sample). In most cases, autoimmune thyroiditis was characterized by changes in the ultrasonographic pattern of the thyroid gland and elevated levels to thyroid peroxidase (TPO) antibodies, while in a quarter of subjects it was accompanied by hypothyroidism. Thyroid nodule was found in 18 athletes, representing 3% of the total sample. In all the thyroid gland nosologies, young males accounted for the majority of the patients, as they were twice as many as young females among those examined. The exception was autoimmune thyroiditis, which was most typical for females (18 girls and 8 boys). Among those diagnosed with thyroid diseases, there were mostly athletes engaged in hockey, swimming, basketball, volleyball, skiing, football.

We analyzed the structure of endocrine disease depending on the sport: the cystic degeneration of the thyroid gland accompanying iodine deficiency was more frequent among hockey players, bobsledders, swimmers, weightlifters; autoimmune thyroiditis - in sambo wrestlers, judokas, badminton players, figure skaters; hypothyroidism - in volleyball players, hockey players, sambo wrestlers, taekwondokas, football players, swimmers, figure skaters; thyroid nodule - in swimmers, bobsledders, hockey players.

The effects of sports loads on endocrine morbidity were determined through the analysis of the data by the intensity of the dynamic and static loads according to J. Mitchell classification [6]. The statistical analysis of the effects of static loads revealed the dependence of thyroid diseases on the maximum group value of MVC (maximal voluntary contraction), while for the dynamic loads - on the maximum oxygen consumption (Max O₂).

Fig. 2. Analysis of morbidity data by intensity of static loads (according to J. Mitchell)

The statistical analysis by the multinomial logistic regression (Fig. 2) showed that the high-intensity static loads increase the probability of iodine deficiency and thyroid nodule. The low-intensity static loads increase the probability of autoimmune thyroiditis and hypothyroidism. The high-intensity dynamic loads increase the probability of hypothyroidism and thyroid nodule. There is a direct correlation between the absence of endocrine disorders and the high level of dynamic loads.

Fig. 3. Analysis of morbidity data by intensity of dynamic loads (according to J. Mitchell)

The multiple correlation analysis revealed a statistically significantly low negative correlation between the level of TTG and sports qualification, which was also confirmed by the Spearman’s non-parametric correlation analysis.

According to a number of surveys, the thyroid gland plays an important role in the physical training process. Thus, according to A.V. Kublov, the basal level of thyroid hormones is higher among athletes, regardless of the nature of physical activity than among non-athletes [3]. The author established a correlation between thyroid status, sports skills level and training process phase. The internal thyroid correlations, according to the author, are beneficial for candidates of sports and masters of sports than for rated athletes, for individuals in the main period of the training process. Regardless of the sport, the sports skills level and training process phase, the thyroid hormone level, which is most pronounced in masters of sports increases in response to physical loads [3]. According to our survey, with the increase in the sports skills level, the level of TTG decreases, indicating improvement in the mechanisms of hormonal regulation of pituitary-thyroid relationships. According to S.D. Megeryan, O.M. Maslennikov, highly-qualified athletes were diagnosed with thyroid nodule three times more often than in the Control Group, which is comparable to the data of our study, 8% were found to have an enlarged thyroid gland [4]. In addition to the clinical studies, the findings of the physiological-biochemical studies made it possible to substantiate iodine deficiency as a factor that limits physical working capacity in the submaximal intensity zone [2], therefore, timely correction of iodine deficiency is a necessary factor in enhancing athletes' physical working capacity and endurance, as well as in preventing the development of such thyroid diseases as hypothyroidism and thyroid nodule.

Conclusion. Due to the high prevalence of thyroid diseases among athletes, a screening assay is required on a regular basis, including thyroid ultrasonography and hormonal status monitoring aimed at the early diagnosis and timely correction of endocrine disorders. The athletic training programs should cover the factors that can lead to endocrine disorders (long-term excessive physical loads, overtraining, breakdown in adaptation caused by steady stresses). Due to the high prevalence of iodine deficiency and associated diseases, athletes need to correct dietary iodine deficiency, which is especially relevant for athletes engaged in sports activities with high static and dynamic physical loads.

References

1. Bobrovnitskiy I.P., Yakovlev M.Yu., Fesyun A.D., Lebedeva O.D., Banchenko A.D. Rating general health and risks of developing common noncommunicable diseases among students in higher education. Russian Journal of Rehabilitation Medicine. 2015. v. 6. No. 1. pp. 3-11.
2. Isaev A.P., Aminov A.S., Erlikh V.V. et al. The Integrative System of Bioelements, Immunological Resistance, Enzyme and Hormonal Activity of Athletes in Conditions of Development of Local Regional Muscle Endurance in Lowland and at Middle Altitude in Different Seasons of the Year. Teoriya i praktika fiz. kultury. 2014. no. 1. pp. 73-79.
3. Kublov A.A., Kichigin V.A., Madyanov I.V. Features of thyroid metabolism in athletes. Zdravookhranenie Chuvashii. 2005. No, 2. pp.21-27.
4. Megeryan S.D., Maslennikova O.M. Features of hormonal status in elite athletes. Fundamentalnye issledovaniya. 2015. No. 1-7. pp. 1370-1373.
5.  Statistical information of the Ministry of Health of Russia [Electronic resource]: Moscow, 2017. https://www.rosminzdrav.ru/ministry/61/22/stranitsa-979/statisticheskie-.... (date of access: 10.12.18).
6. Mitchell J., Haskell W.L., Raven P.B. Classification of Sports. J. Am. Coll. Cardiol. 1994. N. 24. P. 864-866.

Corresponding author: teniaeva@mail.ru

Abstract

Objective of the study was to assess the structure and prevalence of diseases of the endocrine system in athletes based on the in-depth medical examination.
Methods and structure of the study. The study involved an analysis of the medical records of the athletes who had undergone an in-depth medical examination on the basis of Branch 1 of the State Autonomous Healthcare Institution of Moscow Centre for Research and Practice in Medical Rehabilitation, Restorative and Sports Medicine of Moscow Healthcare Department. We analyzed the data from a random sample of medical records of 604 athletes engaged in 48 sports, who had undergone the in-depth medical examination in 2016-2018. We considered the data of sports history, anthropometric measurements, thyroid, abdominal, and pelvic ultrasonography, results of the clinical and biochemical surveys of athletes, hormonal blood spectrum rates (TSH, free T4, prolactin, testosterone, cortisol, TPO antibodies), data of the instrumental survey (ECG, impedance monitoring, echocardiography, cycle ergometer test, spirometry).

Study results and conclusions. The study results indicated a high prevalence of thyroid diseases (in 22% of athletes), which significantly exceeds the data of the overall population. We analyzed the structure of thyroid diseases in the athletes: it was asymptomatic hypothyroidism that was diagnosed most often (in 7.8% of cases); iodine deficiency conditions ran second (6.8%); autoimmune thyroiditis, which was found in 4.3% of all subjects, ranked third, and 3% of athletes were diagnosed with thyroid nodules. The statistical analysis revealed an increase in the probability of iodine deficiency conditions and thyroid nodules under increased static physical loads, and autoimmune thyroiditis and hypothyroidism under low-intensity static loads. With an increase in the intensity of dynamic physical loads, the probability of hypothyroidism and thyroid nodules increases. We found a negative correlation between the level of TTG and sports qualification, which testifies to the improvement of the mechanisms of hormonal adaptation with the enhancement of sports skills. Due to the high prevalence of iodine deficiency and associated diseases, athletes need to correct dietary iodine deficiency, which is especially relevant for athletes engaged in sports activities with the high static and dynamic physical loads.