The review presents generalized epidemiological data on the prevalence of non-neoplastic thyroid pathology in developed and developing countries, in particular in regions with iodine deficiency and the influence of mass iodine prophylaxis on reducing the incidence and prevalence of thyroid diseases in these regions. The data on the prevalence of subclinical hypo- and hyperthyroidism are presented, where according to the averaged data 1 clinical manifestation of thyroid insufficiency accounted for 20 cases of unregistered subclinical hypothyroidism, and 1 case of identified thyroid hyperfunction accounted for 15 cases of subclinical hyperthyroidism. Methodological, clinical and social difficulties in studying the prevalence of thyroid pathology are described. The main nongenomic actions of thyroid hormones, which originated from extracellular domains of cell adhesion protein - integrin αVβ3, resulting in activation of mitogen-activated protein kinase, phosphatidylinositol-3 kinase and serine-threonine-protein kinases, are presented. The ultimate cell and tissue response to this stimulation is the activation of cell proliferation, angiogenesis, cell migration, and increased expression of tissue-specific proinflammatory genes, which ultimately lead to acceleration of the «cancer development and its natural history». Data from epidemiological studies, which established a correlation between thyroid status and incidence (prevalence) of malignant neoplasms, are given. As a result of population-based studies analysis it was demonstrated that long term hyperthyroidism increases the risk of developing malignant neoplasms of different localizations, in particular breast, ovarian, prostate and lung cancer.
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