To study the state of trophoblast and basal membranes of terminal placental villi in pregnant women with compensated diffuse toxic goiter.Placental fragments from 38-40-week pregnant women were investigated by light microscopy and immunohistochemistry using PCNA, NCL-COLL-IV, and NCL-MMP-2-507 monoclonal antibodies ("Novocastra", United Kingdom).Examination of the terminal placental villi revealed changes in their syncytiotrophoblast in the women with physiological and gestosis-complicated pregnancy and compensated diffuse toxic goiter; immunohistochemistry showed degradation of basal membranes and a change in their levels of type IV collagen.In gestosis, compensatory mechanisms occur due to the larger number of symplastic buds and the numerical density of their nuclei and during hormonal imbalance due to the increase in the mean area of symplastic buds. Placental compensatory and adaptive mechanisms in pregnant women with diffuse toxic goiter call for further immunohistochemical investigation of the structural components of the placental barrier.