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Androgens govern the sexual drive but have no effect on its direction, i.e. attraction to a person of the same gender, of the other gender, or indicating a deviant behaviour. It is also possible, albeit not certain, that in parallel they increase the level of aggressivity but only under certain conditions. Testosterone impregnation during the pre- and perinatal phase determines the orientation of the behaviour - and its nature - in adults. Such effects, well observed in animals, are not known in humans. On the contrary, when the human male reaches puberty, androgens stimulate the erotism of the nervous system and trigger the male adult libido. In adults, the rate of testosterone, and even more so that of dihydrotestosterone, could be (discreetly) correlated to sexual activity. Although the administration of testosterone significantly increases the libido of the hypogonadic individual and causes more particularly an increase in the frequency of nocturnal erections, it only has a limited effect on the libido of the normal male. In fact, all studies tend to show that testosterone activates the "unconscious" manifestations of the libido whereas the conscious libido depends on interactions between human beings. Thus, we can understand why males who were castrated before puberty had sufficient libido to enable them to entertain sexual relations without hormonal treatment. We can also understand, if we are ready to accept that when man is sleeping he belongs more to the species than to the individual, that puberty begins with the occurrence, during sleep, of HL-HR peaks controlling those of HL and the secretion of testicular androgens.
It has been demonstrated with women that androgens increase desire as do the estrogens. Even low androgens seem able to stimulate clitoris excitability. The relative character of knowledge concerning the effects of androgens on the libido is a fundamental element, more obvious in women: the role of the androgens on the libido of women still remains very enigmatic.