The Porter Knows

Hypothalamus and Pituitary Gland
The hypothalamus is an area of the brain that controls and influences many automatic functions of the brain through actions on the medulla, and coordinates many chemical or endocrine functions (secretions of sex, thyroid and growth hormones) through chemical and nerve impulse actions on the pituitary gland. Alcohol has two noticeable effects on the hypothalamus and pituitary gland, which influence sexual behavior and urinary excretion.

Alcohol depresses the nerve centers in the hypothalamus that control sexual arousal and performance. As BAC increases, sexual behavior increases, but sexual performance declines. This observation has been known for a long time, and is referred to by William Shakespeare in "Macbeth" (Act 2 scene 3):

    Macduff: What three things does drink especially promote?
    Porter: Marry sir, nose-painting, sleep, and urine. Lechery, sir it provokes, and unprovokes; it provokes the desire, but it takes away the performance...

The porter in the above excerpt also notes the effect of alcohol on urine excretion. Alcohol inhibits the pituitary secretion of anti-diuretic hormone (ADH), which acts on the kidney to reabsorb water. Alcohol acts on the hypothalamus/pituitary to reduce the circulating levels of ADH. When ADH levels drop, the kidneys do not reabsorb as much water; consequently, the kidneys produce more urine.