General Consideration on the P450aro

It is now generally accepted that, at least in rodents, androgens are necessary, during the fetal and/or early neonatal life, to masculinize the hypothalamic centers that control the male-type patterns of gonadotropin and growth hormone secretion (24), as well as

OH OH

OH OH

androstenedione estrone

Fig. 1. The aromatase/17p-hydroxysteroid oxidoreductase (17P-HOR) pathways.

androstenedione estrone

Fig. 1. The aromatase/17p-hydroxysteroid oxidoreductase (17P-HOR) pathways.

those that supervise the expression of male sexual behavior (25,27). Recent data show that this "organizational" effect of androgens may also be present in other species (see ref. 28). A theory, which is now universally accepted holds that the masculinizing effect of androgens is linked to their aromatization to estrogens (1), a process that occurs in several regions of the brain, and especially in the hypothalamus and in the limbic system. In line with this theory, a high aromatizing activity has been found in the medial preoptic area (MPOA) of the hypothalamus, in the sexually dimorphic hypothalamic nucleus, in the limbic system and in the amygdala of fetal and/or neonatal rats and mice (29-33). Estrogens may "masculinize" the brain because of their properties to influence neuronal survival and plasticity, to promote neuronal growth and dendrite arborization, and to facilitate the formation of synapses among hypothalamic neurons (34,35). The conversion of T and androstenedione (ADIONE) into estrogens is also important in some species for inducing some aspects of sexual behavior in adulthood (27).

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