Etiology

Leiomyomas arise from the overgrowth of smooth muscle and connective tissue in the uterus. Evidence of an apparent hormonal dependency includes the following:

Both estrogen and progestin receptors are present in fibroids. Elevated estrogen levels may cause fibroid enlargement. During pregnancy, 15-30% of fibroids enlarge then shrink in puerperium. Fibroids shrink after menopause.