Researches made clear the reason alcohol has an effect on human sexuality as described in Shakespeare's Macbeth, "It provokes the desire, but it takes away the performace."

Reports from Harvard Medical School say that alcohol directly suppresses production of testosterone, a major male sex hormone.

"When alcohol enters gonadal tissues such as the testicles," the report says, "it is broken down by biochemical processes that ordinarily would be used to make testosterone. The oftnoted paradox in male sexual performance during alcohol intoxication may be associated with decreased levels of testosterone."

Then comes the next step. When testosterone levels are lowered in blood following heavy alcohol intake, this decrease signals the brain to activate the pituitary gland （often called the master gland） to secrete a hormone （luteinizing hormone） that stimulates testosterone production. It is believed that this process may be associated with increased sexual desire during alcohol intoxication."

Increased desire, decreased performance – a frustrating scenario for drinkers.

像在莎士比亚的《麦克白》中描述的那样，酒精对人们的性欲会产生影响，"它刺激欲望，但它会影响性能",研究人员对此原因作了澄清。

哈佛医学院的报告称酒精直接抑制了睾丸激素的产量，睾丸激素是一种主要的男性荷尔蒙。

"当酒精进入性腺组织比如睾丸时，"研究中说到，"酒精通过生化过程被分解，分解产物通常会被用来制造睾丸激素。酒精中毒期间男性性行为的矛盾可能与睾丸激素水平的下降有关。"

然后是下一步。当摄入大量酒精后，血液中睾酮水平下降，下降情况会向大脑发出信号刺激脑垂体（常称为主腺）分泌荷尔蒙（促黄体荷尔蒙）,该荷尔蒙会刺激睾丸激素的产生。人们相信这种过程与酒精过量时性欲增长有关。

性欲增长，性能下降--对酒徒而言令人挫败的情景。