The exact cause of uterine fibroids is not known, but several factors may play a role. These factors include:

• Hormones: Two hormones called estrogen and progesterone cause the tissue that lines the inside of the uterus to thicken during each menstrual cycle to prepare for pregnancy. These hormones also seem to help fibroids grow. Fibroids contain more cells that estrogen and progesterone bind to than do typical uterine muscle cells. Fibroids tend to shrink after menopause due to a drop in hormone levels.

• Gene changes: Many fibroids contain changes in genes that differ from those in typical uterine muscle cells.

• Other growth factors: Substances that help the body maintain tissues, such as insulin-like growth factor, may affect fibroid growth.

• Extracellular matrix (ECM): This material makes cells stick together, like mortar between bricks. Fibroids have more ECM than normal cells, which makes them fibrous or ropey. ECM also stores growth factors (substances that spur cell growth) and causes cells to change.

• Race: Black people are more likely to have fibroids than people of other racial groups. Black people have fibroids at younger ages than do white people.

• Age: Fibroids are most common in people of reproductive age.

• Genetics: Having a close relative with fibroids is associated with an increased risk of developing them oneself.

• Weight: Overweight and obesity are associated with an increased risk of fibroids.

Its important to note that having one or more of these risk factors does not necessarily mean that a person will develop fibroids. Fibroids are treatable, and there are effective treatments available, including medication, surgery, or a minimally invasive treatment option known as uterine fibroid embolization.