Also known as Gonadotropin Releasing Hormone, this medication produces a menopause-like state. It prevents the ovary from ovulating and indirectly lowers estrogen levels. As in menopause, fibroids shrink and cause less problems. Symptoms such as cramping and pelvic pain are also reduced. This medication is given by injection once a month and can be continued for up to 6 months. It is very often used to shrink fibroids prior to surgical removal (either by hysteroscope, through the uterus or laparoscope, through the abdomen). The side effects are usually mild and short-lived but include hot flashes, mood disturbances, insomnia, breast discomfort and vaginal dryness. A more serious complication is reduced bone mass when the medication is used over a longer period of time. During treatment with GnRH analogues, woman should take a calcium supplement and consider vaginal lubricants if vaginal dryness persists.

In some cases, bleeding related to uterine fibroids is reduced even after treatment with GnRH analogues is completed.