Alcohol is directly toxic to the testes, causing reduced testosterone levels in men. In a study of normal healthy men who received alcohol for 4 weeks, testosterone levels declined after only 5 days and continued to fall throughout the study period (17). Prolonged testosterone deficiency may contribute to a “femininization” of male sexual characteristics, for example breast enlargement (18). In addition, animal studies have shown that acute alcohol administration affects the release of hormones from the hypothalamus and pituitary (5). Even without a detectable reduction of testosterone levels, changes in these hormones can contribute to the impairment of male sexual and reproductive functions (19). Alcohol also may interfere with normal sperm structure and movement by inhibiting the metabolism of vitamin A (20), which is essential for sperm development. In premenopausal women, chronic heavy drinking can contribute to a multitude of reproductive disorders. These include cessation of menstruation, irregular menstrual cycles, menstrual cycles without ovulation, early menopause, and increased risk of spontaneous abortions (6,21,22). These dysfunctions can be caused by alcohol’s interfering directly with the hormonal regulation of the reproductive system or indirectly through other disorders associated with alcohol abuse, such as liver disease, pancreatic disease, malnutrition, or fetal abnormalities (6). Although most of these reproductive problems were found in alcoholic women, some also were observed in women classified as social drinkers, who drank about three drinks per day during a 3-week study (23). A significant number of these women had abnormal menstrual cycles and a delay or lack of ovulation.
Alcoholic Beverages as a Source of Estrogens
https://pubs.niaaa.nih.gov/publications/arh22-3/220.pdf Alcoholic beverages contain not only alcohol but also numerous other substances (i.e., congeners) that may contribute to the beverages’ physiological effects. Plants used to produce alcoholic beverages contain estrogenlike substances (i.e., phytoestrogens). Observations that men with alcoholic cirrhosis often show testicular failure and symptoms of feminization have suggested that alcoholic beverages may contain biologically active phytoestrogens as congeners. Biochemical analyses have identified several phytoestrogens in the congeners of bourbon, beer, and wine. Studies using subjects who produced no estrogen themselves (i.e., rats whose ovaries had been removed and postmenopausal women) demonstrated that phytoestrogens in alcoholic beverage congeners exerted estrogenlike effects in both animals and humans. Those effects were observed even at moderate drinking levels.
