Estrogen is a steroid hormone produced by the ovaries in women and in small amounts in the testes in men, as well as in fat cells for both sexes. Estrogen functions by signaling to tissues containing cells that produce the estrogen receptor, a protein that binds to circulating estrogen and activates a signal within the cell. Males typically have very low levels of estrogen present in the bloodstream, which can rise as a result of a hormone imbalance or underlying condition, such as obesity. High levels of estrogen in men lead to a number of effects that harm male reproductive health.
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One effect of estrogen on the male body is a condition called gynecomastia, the abnormal growth of breast tissue. In males, the breast tissue contains some glandular tissue that never develops into full breasts. The small amount glandular tissue in the male breast responds to circulating estrogen to proliferate and grow. Breast cells in men with high estrogen levels are continually signaled to divide, so the man will grow breasts.
Males with gynecomastia develop firm breast rich in glandular tissue, which is distinct from pectoral fat deposits that occur in obese men. The University of Maryland Medical Center indicates that some degree of gynecomastia during puberty is normal, and normally goes away on its own. Prolonged gynecomastia can be treated with hormone therapy to treat an underlying hormonal imbalance.
Another effect of estrogen on men is an increased risk of developing prostate cancer. The prostate, a small gland found anterior to the rectum, is part of the male reproductive system. The prostate releases prostate fluid that makes up a part of ejaculate, and cells within the prostate respond to circulating hormones. Prolonged exposure to estrogen or estrogen-mimicking chemicals can cause an increased risk of prostate cancer.
A study published in Journal of Occupational and Environmental Medicine in 2003 studied the levels of environmental estrogens on men with or without prostate cancer. The study found that men with prostate cancer had significantly higher levels of these chemicals in their bloodstream. Furthermore, a study published in the Journal of Molecular Endocrinology in 2007 indicates that natural estrogen promotes prostate cell proliferation and increases inflammation-two processes that promote cancer development.
Another effect of estrogen on men is sterility. Infertility in men can result from low semen production, low sperm count in semen, nonmotile sperm or sperm that cannot survive inside the vagina to fertilize an egg. Stony Brook University indicates that exposure to estrogen in men leads to a decrease in another hormone, FSH, which proves essential in sperm maturation. The University also reports that fetal exposure to estrogen leads to a decrease in the number of sertoli cells, which normally function to support sperm production.