The article reviews current data on autoimmune thyroiditis, its prevalence, factors and mechanisms of
pathogenesis with the participation of various subpopulations of lymphocytes. Particular attention is focused on the
pathomorphological changes occurring in the thyridgland during the progression of this increasingly common disease.
The characteristic features of the white blood picture in autoimmune thyroiditis, in particular absolute and relative
lymphocytosis, are highlighted and described, and an assumption is made to interpret its connection with hyperprolactinemia. The substantiation of the need for early diagnosis and timely therapy of Hashimoto thyroiditis is given in
order to prevent the most dangerous complication — the development of lymphomas.