Effects of estrogens on the testis of transsexuals: a pathological and immunocytochemical study.

Testes from five male-to-female transsexuals removed during sex-reversal surgery after administration of estrogens were studied histologically and with immunoperoxidase procedures to locate estrogen receptors (ER) and related antigens. Atrophy of the seminiferous tubules was observed in all cases; its degree, and a marked decrease in Leydig cells, correlated with low plasma gonadotropin levels (rather than with the duration of treatment). In all cases, the rete testis appeared hyperplastic and the other components (efferent ductules, epididymus) well preserved. The efferent ductules proved to be the only structure where ER can be located by the ER-ICA procedure, whereas staining for the p 29 ER-associated antigen is strongly positive both here and in the rete testis. The immunocytochemical data, in parallel with the observed biological effects, indicate that the rete testis and the efferent ductules and, to a minor degree, the epididymus and Leydig cells are the main direct targets of estrogens in the human testis.