Molecular aspects of steroid hormone action in the male reproductive axis.

Both T and E play important roles in the regulation of reproductive function at the cellular and tissue levels in males. In addition to a causal role in the development of the male reproductive phenotype, androgens provide feedback regulation to the hypothalamus and to the pituitary in humans. Estrogen action is critical for normal bone fusion and mineralization in both men and women, and E action appears to play an important role in hypothalamic suppression of gonadotropin levels.