The aim: The aim of this study was to determine the characteristics of thyroid status (thyroid hormone, total and free fractions of triiodothyronine and thyroxine, reversible triiodothyronine, antibodies to thyroperoxidase) of preschool children with acute bronchitis. Materials and methods: We examined 135 preschool children (from 3 to 6 years old) with acute bronchitis (main group) and 28 apparently healthy subjects who were in the control group. It used clinical-anamnestic, laboratory and instrumental research methods. Evaluation of the course of acute bronchitis was carried out in the acute period of the disease. All results were statistically processed using the SPSS 26 package. Results: In 33 % of patients with acute bronchitis there are subclinical abnormalities of thyroid hormones, which manifest themselves in the form of euthyroid sick syndrome. Namely, we found an increased concentration of reversible triiodothyronine in the serum, as well as a decrease in total triiodothyronine and its free fraction. Conclusions: In patients with acute bronchitis in almost every third case there are functional shifts in hormonal status, which are manifested in the form of the first variant of the euthyroid sick syndrome.

The problem of acute respiratory tract infections (including acute bronchitis) remains urgent in the whole world independent of human age, especially when disease rates are considered. The World Health Organization reports annually on 1.5 billion cases of acute respiratory diseases. In Ukraine, the disease rate is 3.6 times higher among children than among adults (totally, it is equal to 67,000 cases per 100,000 individuals). The highest rate is observed among under-6-year-old children. In contrast to the average bronchopulmonary disease rate in Europe, the same Ukrainian index remains slightly higher for the last decades. Among children, the acute bronchitis rate is 6.2–25.0% within all bronchopulmonary diseases, reaching 50.0–90.0% if there are recurrences. Our literature review aims to compare different researchers’ perspectives, selecting articles and analyzing data as to how thyroid hormones and cortisol influence immune response in children’s bronchopulmonary diseases. In the literature review, the modern perspective of children’s hormonal state in bronchopulmonary diseases is studied. The hypothalamus-hypophysis-thyroid and hypothalamus-hypophysis-paranephros interaction roles in bronchopulmonary adaptive responses are explained. The thyroid hormone and cortisol importance for organism resistance are regarded. The manifestation, pathogenetic progress mechanisms, diagnosing methods, and treatment of different subclinical hormonal shifts (particularly euthyroid sick syndrome) are researched. The interconnection of hormonal and immunological indicators is covered (whose change is a predictively significant marker – that can foresee the disease progress, its duration and consequences for patients). Therefore, the relevance consists in researching the influence of thyroid hormones and cortisol on immune response by different pathological states of children’s bronchopulmonary diseases.