ABSTRACT
The importance of steroid metabolism in the brain is supported by the fact that both the aromatizing and the 5a-reductase pathways are phylogenetically well conserved and can be traced back millions of years. This chapter describes in some detail the most important metabolic pathways involved in mediating the effects of steroid hormones in the developing central nervous system (CNS). It deals with the Aromatase, with the two isoforms of the 5α-reductase (5α-R) and with the 3α-hydroxy steroid dehydrogenase (3α-HSD), taking into account particularly the data obtained in the authors' laboratory. The chapter reviews some data obtained in the authors' laboratory, and others appeared in the literature regarding the interaction between estrogens, androgens, neurotransmitters, and external influences on brain sexual differentiation. Some abnormalities in humans, either pathological or iatrogenic have been studied to evaluate the possible role of fetal androgens on the sexual differentiation of the male brain.
