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What causes uterine fibroids?

Dr. Frederick Friedman, MD
OBGYN (Obstetrician & Gynecologist)

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.

Dr. John C. Lipman, MD
Vascular & Interventional Radiologist

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.

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.

Debra Fulghum Bruce PhD
Healthcare Specialist

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.

Dr. Kevin W. Windom, MD
OBGYN (Obstetrician & Gynecologist)

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.

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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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.