Though rarely used in men, female hormones such as estrogen and progesterone can be taken by males for medical conditions such as testicular cancer, prostate enlargement and aromatase deficiency. Female hormone treatment in men carries a number of risks, because it suppresses the production of testosterone.
Because testosterone is responsible for the development and maintenance of the male sex characteristics, when testosterone levels are opposed by higher levels of female hormones, testosterone will become less effective. Men who take female hormones may be subject to a number of changes affecting the physical state and functioning of the sex organs. These risks may include decreased testes size, lowered sperm count and erectile dysfunction along with loss of libido. In addition, men taking female hormones may develop gynecomastia, or the growth of breast tissue in men, along with darkening and enlargement of the nipples.
Testosterone is primarily responsible for the development of muscle mass and bone tissue in men. With female hormone usage, large muscle groups such as the chest, legs and arms may begin to shrink and bones may become more porous and brittle, thereby contributing to weakness and bone fracture. In addition, fat storage in men who take hormones may be increased, leading to a feminization of body shape. Facial and body hair may begin to grow more slowly; however male pattern baldness may improve as it is primarily caused by a metabolite of testosterone.
As testosterone is a male hormone, thought to play a factor in assertiveness and aggression, men who take female hormones may become less assertive. Some men may lose interest in previously pleasurable activities, including sex. These changes may reverse themselves once the female hormones are discontinued, but some men may develop depression from both the use of hormones and from self esteem issues that may arise from physical changes. Some men may experience hot flashes, similar to those seen during menopause as well as other problems such as insomnia and forgetfulness.
Increased Disease Risk
As breast tissue is developed, there may be a corresponding increase in the risk of breast cancer. There is also an increased risk of stroke due to the development of clots related to female hormone usage, particularly among smokers, but a decreased chance of heart attack is probable. An increased chance of the development of liver and gall bladder disease may be seen; however a decreased risk in the development and growth of prostate enlargement and prostate cancer is possible.