Female birth control pills are intended to prevent contraception in women. They are most often a combination of synthetic forms of both types of female hormones, estrogen and progesterone. Although rarely used, female hormones may be taken by men for a number of medical conditions such as prostate enlargement, testicular cancer and aromatase deficience. Because oral contraceptives are not intended for use in men, side effects have not been well studied or documented; however, they may cause a number of adverse effects in men similar to those seen with the use of other female hormones.
Testosterone is responsible for the formation and development of male sex characteristics. When testosterone is opposed by high levels of female hormones present in birth control pills, testosterone will be less effective. Men who take female birth controls may experience changes in the functioning and physical appearance of their sex organs. Risks may include lowered sperm count, decreased libido, erectile dysfunction and shrinking testes size. Some men may also develop breast tissue, known as gynecomastia, along with enlargement and darkening of the nipples.
Testosterone is largely responsible for the greater growth of muscle tissue and bone tissue in men. With the use of female birth control pills, testosterone will be less effective, and large muscle groups such as the legs, chest and arm muscles, may decrease in size. In addition, the bones may develop a condition similar to osteoporosis, becoming more porous and brittle. This may increase the risk of bone fracture. Fat storage may also be affected, leading to a feminization of the physical appearance. Facial and body hair may also decrease in thickness and growth, although male-pattern baldness may improve somewhat.
Testosterone is thought to play a role in male assertiveness and aggressive tendencies. As testosterone effectiveness is decreased by taking female hormones such as birth control pills, men may become less assertive. Some men may also lose interest in sex and other pleasurable activities while taking female birth control pills, due to both hormonal influence but also because of depression that may develop from self-esteem issues related to physical changes. Hot flashes and other symptoms such as insomnia and foggy thinking, usually experienced by women, may also occur.
The development of breast tissue may increase the risk of the development of male breast tissue. Birth control pill usage may also increase the risk of the development of hormone-related blood clots, particularly in those who smoke. Men who take female hormones, including birth control pills, may also increase the chance for developing liver and gallbladder disease. There may be, however, a decrease in the chance of prostate enlargement and cancer.