Testosterone effects can impact bodily growth and function in many ways in men. Naturally producing lots of testosterone or taking supplementary doses can lead to increases in muscle mass, weight, body hair, and changes in sex drive. In excess, some evidence suggests that the hormone can cause severe headaches, heart problems, psychological issues such as lowered sperm count, bouts of rage or depression.
Testosterone effects can also occur if the body is not producing an adequate level of the hormone in men. This can result due to aging, health issues leading to the removal of one or both testicles, or a malfunction in the production glands that simply prevents the body from creating an adequate supply.
Low testosterone can delay the onset of puberty, slow rates of growth and muscle gain, and effect sexual desire and performance.
As with men, high testosterone levels greatly increase protein absorption and muscle-building capability, but may also lead to facial hair, a deepened voice, and acne. Menopausal women are occasionally prescribed low doses of testosterone to increase libido and prevent bone density loss due to osteoporosis.