What Are Uterine Fibroids?
A uterine fibroid is the most common benign (not cancerous) tumor of a woman's uterus (womb). Fibroids are tumors of the smooth muscle found in the wall of the uterus. They can develop within the uterine wall itself or attach to it. They may grow as a single tumor or in clusters. Uterine fibroids can cause excessive menstrual bleeding, pelvic pain, and frequent urination.
- These growths occur in up to 50% of all women and are one leading cause of hysterectomy (removal of the uterus) in the United States. An estimated 600,000 hysterectomies are performed in the US annually, and at least one-third of these procedures are for fibroids. Medications and newer, less invasive surgical treatments are now available to help control the growth of fibroids.
- Fibroids start in the muscle tissues of the uterus. They can grow into the uterine cavity (submucosal), into the thickness of the uterine wall (intramuscular), or on the surface of the uterus (subsersoal) into the abdominal cavity. Some may occur as pedunculated masses (fibroids growing on a stalk off of the uterus).
- Although these tumors are called fibroids, this term is misleading because they consist of muscle tissue, not fibrous tissue. The medical term for a fibroid is leiomyoma, a type of myoma or mesenchymal tumor.
What Causes Uterine Fibroids?
The exact reasons why some women develop fibroids are unknown. Fibroids tend to run in families, and affected women often have a family history of fibroids. Women of African descent are two to three times more likely to develop fibroids than women of other races.
Fibroids grow in response to stimulation by the hormone estrogen, produced naturally in the body. These growths can show up as early as age 20, but tend to shrink after menopause when the body stops producing large amounts of estrogen.
Fibroids can be tiny and cause no problems, or they also can grow to weigh several pounds. Fibroids generally tend to grow slowly.
The following factors have been associated with the presence of fibroids:
- Being overweight, obesity
- Never having given birth to a child (called nulliparity)
- Onset of the menstrual period prior to age 10
- African American heritage (occurring 3-9 times more often than in Caucasian women)
Medically Reviewed by a Doctor on 11/21/2017
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