When a woman has too much testosterone in her system, there are a few telltale symptoms: acne, irregular periods and weight gain. Elevated testosterone levels also cause acanthosis nigricans, a condition in which patches of dark skin appear on the back of the neck or other areas. It can also cause hirsutism, which is extra hair on the face or other parts of the body where thick hair normally doesn't grow [source: Center for Young Women's Health]. And, in the case of opposite-sex twins, testosterone exposure can even affect the odds a woman will someday marry. Researchers in England discovered adult female twins were 15 percent less likely to marry if they had a male twin and were 25 percent less likely to have children -- all attributed to in utero testosterone exposure [source: ScienceDaily].
When men have too much testosterone coursing through their veins, problems also arise. Too much of the chemical compound, and it can cause liver disease, while boosting levels of bad cholesterol and lowering levels of good cholesterol -- which can lead to heart disease. And, as excess testosterone naturally undergoes a chemical conversion within the body, it can cause acne and male-pattern baldness [source: Harvard Medical School].