Thyroglobulin is a marker of relapse of differentiated thyroid cancer. Currently, several B-cell epitopes have been identified in the composition of thyroglobulin using peptides containing individual antigenic determinants of TG. However, the immunopathogenetic role of these epitopes remains not entirely clear, and its study is promising for further research. Currently, the 3-dimensional structure of TG is unknown, but at the same time, the 3-dimensional structure of acetylcholinester (AChE) is known, on the basis of which it is possible to construct a mathematical model of the C-terminal region of TG, homologous to AChE. It has been shown that autoantibodies to the epitopes of TG M4-814, TgP15, 2376-2464, TgP26, and TgP41 are detected in 80%, 0%, 10%, and 7% of patients with Hashimoto's thyroiditis; in 50%, 22%, 100%, 29%, and 34% of patients with Graves' disease; and practically absent in healthy donors (Gentile F. et al.). Therefore, from the described TG epitopes, we selected five epitopes related to the C-terminal AChE, a similar region of TG, and recombinant proteins were constructed. From a collection of monoclonal antibodies to TG obtained in the laboratory, 10 mAbs interacted with recombinant AChE immobilized on the surface of the wells of polystyrene plates. Only blood sera from patients with diffuse toxic goiter and autoimmune thyroiditis with minimal levels of antibodies to TG (more than 500 IU/ml) reacted with AchE. Conclusion: in models of a fragment of the TG molecule homologous to AChE, the AG-AT bond sites remain the most probable.