THE ROLE OF SEX HORMONES 
During childhood, the capacity of sexual response and the experience of sexual pleasure as well as the potential for orgasm exists at least in a proportion of children whether this apparently variable potential among childrenreflects different learning experiences during childhood, different opportunities for realizing the potential or different gentile influences is not known. The importance of gonadal hormones in particular testosterone, in organizing early brain development and function has been discussed earlier. During childhood, gonadal steroid hormones are title in evidence, but from the ages of 9 or 10 years they start to increase as the child approaches puberty from there on we have to consider the activating role of those hormones on sexuality and the impact they have on sexuality, and the impact they have on sexuality, and the impact they have on sexuality during three stages of the life course around puberty and during early adolescence during adulthood until muddle age, and during the later years. 
An adult male’s continued interest in sex depends on he’s having a normal level of circulating testosterone. If an otherwise normal male has his testosterone lowered by testicular suppressive drugs, he experiences a decline in sexual interest, which returns when the process is reversed. In case of testicular impairment (primary or secondary hypogonadison). When testosterone level fall below normal range almost all males experience a decline in sexual interest and capacity for ejaculation. This is reversed by testosterone replacement the raphy. This is a robust, predictable finding across a substantial number of placebo-controlled studies. A similar pattern is observed with spontaneous erection during sleep, or nocturnal penile tumescence, which decline and return with testosterone withdrawal and replacement these erections are interesting manifestations of the sexually arousability of the brain uncomplicated by cognitive processes, and this evidence clearly points to the role of testosterone in central sexual arousal mechanism it is important to emphasis, however, that normal levels of testosterone are necessary but not sufficient for normal levels of sexual desire. These are the factors which can inhibit or alter sexual desire in the presence of normal testosterone levels. 
The role of testosterone the become less clear as men get older there is a normal, but variable, tendency for tester one levels of decline on men beyond the fifth decade, and this is often accompanied by an age-related decline in sexual interest. This is sometimes referred to inappropriately as the “male menopause” However, there is no clear evidence that that this pattern can be reversed by testosterone replacement. It is possible that there is a decline in responsiveness to testosterone in addition to a fall in the hormone level (Schiavs, 1999). 
There is also a common (though variable) age-related decline in erectile responsiveness, such that are men get older erections develop less consistently and are less strong and less well-sustained. The mechanisms for this are not well understood but may be related to change in neuro transmitter responsiveness in erectile tissues (Cerner and Chirst, 2000).
THE SIDE EFFECTS OF DRUGS
Given the complexity of the brain, and its mechanism of control, it is not surprising that anyone mechanism in  involved in a variety of different response patterns. Thus mechanisms relevant to control to sexual response may also be relevant to control of other motivated behaviours such as eating or aggressive behaviour for this season it is difficult to develop drugs which selectively influence specific aspects of brain function. As a consequence, drugs developed for one purpose have other unwanted or unintended side effect. Sexual side effects of drugs aimed at the as are not uncommon although biochemical mechanisms in the CNS are enormously complex, as previously discussed, we can consider drug effects which are likely to be predominantly central and those repdominantly peripheral. We can also consider drugs which have serotonergic, noradrenergic, and dopaninergic effects. The best examples are modery anticlegressanys which involve inhibition of serotonin re-take (SSRI’S such as flutxcline; Rosen, lane, & menace (2001). Such drug commonly inhibit organism in women or decay ejaculation in men, and are used to treat problems of repaid ejaculation.