The causes of uterine leiomyomata, or uterine fibroids, are not yet well understood by physicians and researchers. Fibroids are non-cancerous tumors, or growths, that develop along the lining of the uterine wall during a woman’s childbearing years. They are the leading cause of hysterectomies in the United States. About 50 to 80 percent of women develop fibroids by age 35, although many are asymptomatic. In his book, “100 Questions and Answers About Uterine Fibroids,” Dr. Lloyd Greig writes that no single theory explains why fibroids develop or why some go undetected while others cause serious health issues. Dr. Greig is a gynecologist practicing in Beverly Hills, Calif. Although the causes of fibroids in the uterus are not clearly defined, there are certain factors that predispose some women to developing the growths.
Race
African-American women are three times more likely than white women to develop fibroids. They also develop fibroids at an earlier age than white women and their tumors tend to be larger. As of 2010, there is no definitive study that answers why, but in the December 2008 issue of “Proceedings of the National Academy of Sciences,” Dr. Shyamal D. Peddada notes that most of the African-American women in his fibroid tumor study had high body mass index numbers. A high BMI correlates to a high percentage of body fat, and obesity is also risk factor in developing uterine fibroids. Dr. Peddada is a principal investigator with the National Institutes of Health.
Obesity
Obesity is strongly related to a higher incidence rate of fibroids in the uterus. A 1986 study published in the "British Medical Journal" reveals that for every 22 pounds over 121 pounds, a woman’s likelihood of developing fibroids increases by 21 percent. This means that a woman who weighs 154 pounds or more is three times more likely to develop fibroids than a woman who weighs 121 pounds or less.
Genetics
While scientists have not yet identified a specific fibroid tumor gene, there appears to be a genetic component to the development of uterine fibroids. Women who have a close relative with fibroids are more likely to have fibroids themselves than women who do not have a familial connection, 59% versus 41%. In cases of identical twins, if one twin is diagnosed with uterine fibroids, the other twin is twice as likely to also develop fibroids. This is not the case with fraternal twins.
Estrogen and Progesterone
Estrogen and progesterone are hormones that stimulate the development of female sex traits and control the menstrual cycle. The fact that fibroid tumors have not been reported in premenstrual girls suggests that these sex hormones are related to the development of fibroids. After menopause, when these hormone levels fall, fibroids often shrink or sometimes disappear.
References
- “100 Questions and Answers About Uterine Fibroids”; Lloyd Greig, M.D.; March 2010
- “Journal of the American Medical Association”; Uterine Fibroids; Carolyn J. Hildreth, M.D.; January 2009
- “Proceedings of the National Academy of Sciences”; Growth of Uterine Leiomyomata Among Premenopausal Black and White Women; Shyamal D. Peddada, Ph.D.; December 2008
- “British Medical Journal”; Risk Factors for Uterine Fibroids: Reduced Risk Associated with Oral Contraceptives; Ronald K. Ross, M.D., August 1986
- “Interventional Radiology in Women's Health”; Gary P. Siskin, M.D.; April 2009
