The endocrinology of sexual arousal.Testosterone, a hormone produced primarily in the testicles, plays a critical role in a man's life experience. It helps maintain bone density, fat distribution, sperm production, muscle strength and mass, and red blood cell production. When it ebbs, testosterone also makes itself felt; low testosterone levels may cause physical changes, such as increased body fat, reduced muscle bulk and strength, and decreased bone density. In some cases, testosterone replacement therapy may be prescribed in the male sexual arousal hormones of injections, pellets, patches, or gels to improve the symptoms of low testosterone. Testosterone levels peak in the late teens and then gradually decline over time, typically about one percent a year after age By age 60 to 65, though usually earlier, most men notice that their sexual inclinations and sexual abilities have changed; it takes longer for the penis to become erect and their erections may not be as firm. It may also take longer to male sexual arousal hormones orgasmic and ejaculatory thyroid hormone levels low.
The endocrinology of sexual arousal. - PubMed - NCBI
The relevance of testosterone, oestradiol and certain peptides oxytocin OT , beta-endorphin and prolactin PRL to sexual arousal in humans is reviewed. In addition to behavioural studies, evidence of distribution of gonadal steroid receptors in the brain and the limited evidence from brain imaging are also considered. Testosterone plays a key role in the adult male, with clear, consistent evidence from studies of hypogonadal and eugonadal men. The roles of testosterone in the development of sexual arousability, and in the aging male, are less clear.
The relevance of aromatization and of non-sexual effects of testosterone which might indirectly influence sexual arousal are not well understood. Testosterone in the female presents a more complex, less consistent picture. One possible explanation is a much greater variability across women in responsiveness to testosterone. A 'desensitization hypothesis' to account for the striking gender differences is offered. There is limited evidence of a direct effect of oestradiol on sexual arousability in women.
The extent to which testosterone in women acts by conversion to oestradiol or by increase of free oestradiol is not yet clear. The role of peptides in sexual arousal remains uncertain, partly because of the multiple roles and sites of action of most peptides. OT and beta-endorphin appear to have both excitatory and inhibitory effects. PRL has been proposed as an inhibitory factor via direct inhibition of dopaminergic activity, but the evidence for this is inconclusive.
Whereas the traditional concept of 'hormone' continues to apply to the role of testosterone and oestradiol in sexual arousal, peptides present a more complex role. National Center for Biotechnology Information , U.