Lupron is a synthetic hormone that causes a "chemical menopause" with a marked reduction in estrogen levels. This drug effectively shrinks fibroids and the overall uterine size by up to 50%. The drug works by shrinking the blood supply of the fibroids. Unfortunately, the effect is only temporary as fibroids rapidly regrow following cessation of the drug. Side effects usually limit the use of lupron to a few months. During UFE it is desirable to have enlarged blood vessels feeding the fibroids so there is a more effective embolization of the tumors. Therefore, it is recommended that UFE be postponed until at least 8 weeks after the last lupron injection.