The monograph by O. Reznikov is based on the results of many years of experimental research by the author and his scientific team. It covers a wide range of problems of the etiology and pathogenesis of disorders of neuroendocrine regulation of reproduction, behavior, and the state of the hypothalamic-pituitary-adrenocortical system (HPAS), which are caused by epigenetic changes in the brain at the early stages of ontogenesis. As pathogenic factors affecting the development of the fetal neuroendocrine system during intrauterine development or immediately after birth or during puberty, the author considers hormonal imbalance, stress, endocrine disruptors of chemical origin, and some drugs. Special attention is paid to the sexual differentiation of the brain under normal and pathogenic conditions.