What causes uterine fibroids?

Amanda S. Hess, DO
OBGYN (Obstetrics & Gynecology)
In this video, OBGYN Amanda Hess, MD, at Frankfort Regional Medical Center, explains possible causes and describes the different types of uterine fibroids.
Rafael J. Perez, MD
OBGYN (Obstetrics & Gynecology)
Up to 75% of women in the United States will develop fibroids at some point in their life, typically during their childbearing years. No one knows what causes fibroids. Research has shown several possibilities, but a specific genetic marker has not yet been identified. Identifying any gene that causes fibroids will allow doctors to tell women if they are prone to getting fibroids and steps to take to prevent the growths from affecting quality of life. Research into the cause of fibroids is ongoing.

Uterine fibroids can grow as a single tumor or you can have many. They can be as small as an apple seed or as big as a grapefruit. The growths can cause significant pain, bleeding and fertility problems. 
Frederick Friedman, MD
OBGYN (Obstetrics & Gynecology)
Uterine fibroids are actually smooth muscle tumors. They are almost always benign, although they can grow to rather large sizes. While the exact cause is not known presently, recent molecular genetics studies have implicated a series of genes that may be responsible for their growth. Clearly there appear to be genetic factors involved because fibroids tend to run in families; there are racial predilections as well. Hormones also appear to play a role - estrogen and progesterone receptors have been demonstrated on fibroids. In addition, fibroids tend to grow during a woman's reproductive years, as estrogen is produced. After menopause, when estrogen levels decline, fibroids tend to shrink.
No one knows for sure what causes fibroids. Researchers think that more than one factor could play a role. These factors could be:
  • Hormonal (affected by estrogen and progesterone levels)
  • Genetic (runs in families)
Because no one knows for sure what causes fibroids, we also don't know what causes them to grow or shrink. We do know that they are under hormonal control -- both estrogen and progesterone. They grow rapidly during pregnancy, when hormone levels are high. They shrink when anti-hormone medication is used. They also stop growing or shrink once a woman reaches menopause.

This answer is based on source information from National Women's Health Information Center.
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No one know what causes fibroids. They are typically seen in women of child-bearing age and more common in African-American women than women of other racial groups.
Each uterine fibroid begins its development as a single muscle cell and for unknown reasons begins to duplicate. While it is not known what causes fibroids to grow, these tumors are under the control of estrogen and progesterone, the principal ovarian hormones. After menopause, when the estrogen levels fall, fibroids decrease in size. 

The exact cause of uterine fibroids is unknown, but doctors know that it develops in smooth muscle tissue that's found in the uterus. When one cell reproduces over and over again, it forms a growth called a myoma, or a uterine fibroid. The reason for this random cell reproduction isn't clear, but it may be related to genetic mutations, elevated levels of hormones like estrogen and progesterone, and other chemicals found in the body.

Kevin W. Windom, MD
OBGYN (Obstetrics & Gynecology)
The cause of uterine fibroids is not known.  Most fibroids occur in women of reproductive age, and it is thought that hormones play a role in the growth of these benign tumors of the uterus.  Genetics definitely plays a role in the cause of fibroids, and it is well known that African American women have a much higher instance of fibroids.  Lastly, it is rare to see fibroids occur in a young woman who has not started menstruating as well as in a woman who has gone through menopause.

Continue Learning about Uterine Fibroids

Uterine Fibroids

If you have uterine fibroids, you may never even notice that they are there. Ranging from the size of a small seed to grapefruit-sized, fibroids are tumors on the uterus that rarely cause harm. Some women have true discomfort with ...

fibroids, including pain in the abdomen or low back, or pain during sex. Sometimes, uterine fibroids can cause miscarriage, preterm labor, or even lead to infertility. Women in their 40s and 50s, women of African-American descent and women that are overweight are at higher risk of developing fibroids, although an estimated 20-80% of women will have them at some point before they turn 50. If your doctor notices fibroids during an ultrasound or pelvic exam, he or she may want to treat them with medication or surgery.

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.