Drug Information

Gonadotropin-Releasing Hormone Analogue (GnRH-A) Therapy

Gonadotropin-Releasing Hormone Analogue (GnRH-A) Therapy


gonadotropin-releasing hormone analogue (GnRH-a)

Generic Name Brand Name
goserelin acetate Zoladex
leuprolide Lupron, Lupron Depot
nafarelin Synarel
  • Goserelin (3.6 mg pellet) is injected under the skin of the abdomen (subcutaneously) once every 28 days. The pellet is gradually absorbed by the body.
  • Leuprolide is injected into a muscle (intramuscularly) once a month. It is also available in a dose that lasts for 3 months.
  • Nafarelin is sprayed into the nose (intranasally) twice a day.

Gonadotropin-releasing hormone analogue (GnRH-a) therapy is approved for the treatment of endometriosis and uterine fibroids. A GnRH-a is rarely used for dysfunctional uterine bleeding.

To avoid long-term side effects, GnRH-a therapy is usually taken for only 3 to 6 months.

How It Works

GnRH-a therapy decreases the production of the hormone estrogen  to the levels that women have after menopause . This decrease:

  • Prevents ovulation  and stops menstrual periods (but it does not provide dependable pregnancy prevention).
  • Stops the growth of and reduces the size of endometriosis sites (implants).
  • Reduces uterine size.
  • Stops uterine fibroid growth and promotes fibroid shrinkage. 1

Why It Is Used

GnRH-a therapy is used to help diagnose or treat disorders that are linked to menstrual hormones, such as endometriosis and uterine fibroids. GnRH-a therapy may be used:

  • For dysfunctional uterine bleeding or ovarian cysts .
  • For endometriosis.
  • When an ultrasound  has confirmed that uterine fibroids are present and they cause significant symptoms.

Dysfunctional uterine bleeding. GnRH-a therapy is used under special circumstances, such as when no other medical treatment has reduced uterine bleeding and a woman wants to avoid surgery.

GnRH-a therapy is sometimes used to thin the endometrium  before endometrial ablation  for dysfunctional uterine bleeding.

GnRH-a is a good choice for women who have heavy menstrual periods after organ transplant procedures, especially a liver transplant. If it is used for long-term therapy after organ transplant, then additional treatment with daily estrogen andprogesterone  is recommended to prevent bone loss ( osteoporosis ). This is called “add-back” therapy.

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Uterine fibroids. GnRH-a therapy is usually limited to presurgery treatment to:

  • Shrink fibroids before removal by myomectomy  or hysterectomy .
  • Correct anemia  caused by heavy bleeding. (Iron supplements are another option for correcting anemia.)

GnRH-a therapy is not usually used to relieve fibroid symptoms only, because fibroids grow back fairly quickly after GnRH-a therapy ends. But for women who are close to menopause (when fibroids shrink), short-term relief with GnRH-a therapy may be a reasonable option.

Before gynecologic surgery. GnRH-a therapy may be used before surgery to: 1

  • Reduce the size of fibroids or endometriosis sites (implants). This allows for easier removal of the problem growths or the uterus (hysterectomy).
  • Attempt to prevent scarring that might occur after surgery.

GnRH-a therapy is usually used for short periods of time (3 to 6 months). It can weaken the bones when used for longer periods of time.

How Well It Works

Dysfunctional uterine bleeding. GnRH-a therapy causes a significant reduction in severe menstrual bleeding. This relieves anemia and reduces the need for blood transfusions . But blood loss returns to pretreatment levels when this treatment is stopped.

Uterine fibroids. Fibroids usually shrink to 35% to 65% of their original size. 1

  • Smaller fibroids are easier to remove surgically (myomectomy).
  • Smaller fibroids result in fewer surgical complications and less blood loss during surgery.
  • Small fibroids may completely disappear after 12 weeks of treatment.
  • A vaginal hysterectomy may be possible, which would avoid an abdominal hysterectomy.

Ovarian cysts. GnRH-a therapy may reduce or prevent ovarian cysts that are related to ovulation.

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Chronic pelvic pain. Women report improvement in pelvic pain at the end of treatment with:

  • Leuprolide (Lupron Depot).
  • Nafarelin (Synarel).


  • These medicines are only a temporary solution. When treatment stops, chronic pelvic pain and fibroid growth will gradually return until menopause.

Side Effects

All medicines have side effects. But many people don’t feel the side effects, or they are able to deal with them. Ask your pharmacist about the side effects of each medicine you take. Side effects are also listed in the information that comes with your medicine.

Here are some important things to think about:

  • Usually the benefits of the medicine are more important than any minor side effects.
  • Side effects may go away after you take the medicine for a while.
  • If side effects still bother you and you wonder if you should keep taking the medicine, call your doctor. He or she may be able to lower your dose or change your medicine. Do not suddenly quit taking your medicine unless your doctor tells you to.

Call 911 or other emergency services right away if you have:

  • Trouble breathing.
  • Swelling of your face, lips, tongue, or throat.

Call your doctor if you have:

  • Hives.
  • A fast or irregular heartbeat.
  • Bone, muscle, or joint pain.
  • Anxiety, depression, or other mood changes.
  • Bleeding between menstrual periods.

Common side effects of this medicine include:

  • An irregular menstrual period (or no menstrual period at all).
  • Hot flashes.
  • Vaginal burning, itching, or dryness.
  • Decreased sexual interest.
  • Thinning of the bones.
  • Increased acne or oily skin or hair.
  • An irritated or runny nose (nafarelin only).

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Many doctors are prescribing GnRH-a therapy in combination with other medicines such as low-dose estrogen and progestin to control bone-thinning and decrease menopausal side effects, such as hot flashes. Add-back therapy is usually started if you need to be on GnRH-a therapy for more than 3 to 6 months.

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Taking medicine

Medicine is one of the many tools your doctor has to treat a health problem. Taking medicine as your doctor suggests will improve your health and may prevent future problems. If you don’t take your medicines properly, you may be putting your health (and perhaps your life) at risk.

There are many reasons why people have trouble taking their medicine. But in most cases, there is something you can do. For suggestions on how to work around common problems, see the topic Taking Medicines as Prescribed.

Advice for women

Do not use this medicine if you are pregnant, breast-feeding, or planning to get pregnant. If you need to use this medicine, talk to your doctor about how you can prevent pregnancy.


Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor if you are having problems. It’s also a good idea to know your test results and keep a list of the medicines you take.




  1. American College of Obstetricians and Gynecologists (2008, reaffirmed 2012). Alternatives to hysterectomy in the management of leiomyomas. ACOG Practice Bulletin No. 96. Obstetrics and Gynecology, 112(2, Part 1): 387–399.

Last Revised: July 1, 2013

Author: Healthwise Staff

Medical Review: Sarah Marshall, MD – Family Medicine & Andrew Swan, MD, CCFP, FCFP – Family Medicine & Divya Gupta, MD – Obstetrics and Gynecology, Gynecologic Oncology