Male Sex Hormones in Andrology Today

AbstractSeveral hormonal pathways are deeply involved in the regulation of male sexual function. Testosterone (T) is involved in the modulation of all steps of sexual response from the activation (sexual desire) to the resolution (orgasm and ejaculation). Androgen receptors are deeply expressed in several brain areas involved in the control of sexual response as well as in the male genitalia tract and corpora cavernosa. At these levels, T plays a crucial role in all pathways of penile erection, including nitric oxide (NO) production and degradation, adenosine signaling, calcium sensitization, and penile smooth muscle differentiation. In addition, T is also involved in the control of ejaculatory reflex modulating male genitalia tract contractility and semen bolus expulsion. The role of other sex steroids is more limited, although estrogens seem to partially regulate male sexual desire. Thyroid system is mainly involved in the control of the ejaculatory reflex, although a possible contribution in the modulation of sexual desire and penile erection has also been supposed. Available evidence suggests that prolactin (PRL) acts in the control of sexual desire either through indirect (inducing secondary hypogonadism) or direct mechanisms (modulating dopamine and serotonin central pathways). The role of other hormonal pathways in the regulation of male sexual response appears negligible.