What causes fibroids?
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.
Doctors and medical researchers do not know what causes fibroids to develop. However, evidence suggests that the female hormones, estrogen and progesterone, can make fibroids grow. During pregnancy, when the hormone levels are high, fibroids tend to increase in size. After menopause, when the hormone levels are low, fibroids stop growing and may become smaller.
