The pathogenesis of diffuse toxic goiter has not yet been fully understood. The literature increasing commonly focusses on the issues related to the processes occurring in the thyroid gland itself: proliferation, apoptosis, and angiogenesis. Objective: to investigate clinical and laboratory parameters, as well as the expression of Ki-67, Bcl-2, Bax, Fas-L, CD34, VEGF, and FGF proteins in various postoperative outcomes of patients operated on for diffuse toxic goiter. Subjects and methods. The investigation enrolled 24 women who had undergone surgery using the technique described by E.S. Drachinskaya. Immunohistochemical tests were carried out according to the standard protocol. The expression of Ki-67, Bcl-2, Bax, Fas-L, CD 34, VEGF, angiopoietin, and FGF proteins was determined. Results. The patients with postoperative thyrotoxicosis were ascertained to have a significantly greater expression of anti-apoptotic protein Bcl-2, proliferation marker Ki-67, vascular factors (FGF, VEGF), and CD 34. Conclusion. The relative expression area of the anti-apoptotic protein Bcl-2 of more than 2.19 or the proliferation protein Ki-67 of more than 1.059 was found to predict the development of postoperative thyrotoxicosis with an accuracy of higher than 85%.