A complex constitutional-endocrinological investigation of persons of both sexes with clinical diagnosis of transsexualism (TS) has been held. On the basis of original data some peculiarities of somato- and cerebrotypes of transsexuals have been revealed, the formation of these peculiarities is significantly connected with the action of sexual hormones. A disturbance in ratio of male and female sexual hormones in the direction of predominance of the hormones corresponding to the patient's sexual autoidentification despite their biological sex has been marked. It gives possibility to consider that TS pathogenesis is undoubtedly connected with inborn pathology of hormonal homeostasis. The results of multi-disciplinary approach to study of TS are being discussed. An assumption about the role of disturbance in the system of "hormones-brain" in the TS origin is given.