The etiology (origin and causes) of uterine fibroids is unclear. It is believed that uterine fibroids are associated with hormone levels, because they rarely occur before menarche (onset of menstrual cycle) and usually decrease in size and symptoms after menopause. Furthermore, family history, genetics and lifestyle, such as diet, weight and cholesterol levels, likely play a role in uterine fibroids, although their connection is not well established.