How Do Gonadotropin Releasing Hormone Antagonists Work?

Gonadotropin releasing hormone (GnRH) antagonists are medications used to treat certain conditions that affect the reproductive system in women, including infertility, endometriosis, and uterine fibroids. GnRH antagonists work by blocking the activity of GnRH, a hormone secreted by the hypothalamus.

GnRH stimulates the pituitary gland to release follicular stimulating hormone (FSH) and luteinizing hormone (LH), which work in fine coordination to stimulate ovulation and ovarian production of estrogen and progesterone, the hormones that help the growth and release of the ovum, and subsequently, implantation and maintenance of pregnancy.

GnRH antagonists block pituitary gland stimulation by binding to GnRH receptors in the pituitary gland. This prevents the release of LH and FSH and the resultant ovarian production of estrogen and progesterone. GnRH antagonists work in the following ways:

• In infertility treatment, after the stimulation of follicular growth, GnRH antagonists help delay the luteinizing hormone surge and prevent ovulation until the follicles are of adequate size.
• Reduction in estrogen production by the ovaries helps relieve endometriosis symptoms and shrink the endometrial tissue. Endometriosis is an abnormal growth of endometrial tissue outside the uterus, which goes through cyclic growth and breakdown, causing internal bleeding, inflammation, and scarring.
• By lowering the blood concentration of estrogen and progesterone, GnRH antagonists reduce bleeding associated with uterine fibroids. In uterine fibroid treatment, GnRH antagonists are typically combined with synthetic estrogen and progestin to replace the loss of natural hormones.

The FDA-approved of uses of gonadotropin-releasing hormone antagonists include the following:

• Infertility treatment in adult women, administered as subcutaneous injections at the appropriate phase of the cycle to achieve ovulation
• Management of moderate to severe pain from endometriosis in adult women, administered as tablets every day, with treatment duration not exceeding 24 months
• Management of heavy menstrual bleeding associated with uterine leiomyomas (fibroids) in premenopausal women, administered as capsules every day, with treatment duration not exceeding 24 months

Side effects of gonadotropin-releasing hormone antagonists may include the following:

• Headache
• Nausea
• Ovarian hyperstimulation syndrome
• Hot flashes
• Night sweats
• Decreased bone mineral density
• Raised blood pressure
• Vaginal bleeding
• Pelvic pain
• Amenorrhea (absence of menstruation)
• Metrorrhagia (vaginal bleeding between periods)
• Fatigue
• Insomnia
• Mood swings, altered mood
• Depression, depressed mood, or tearfulness
• Anxiety
• Irritability
• Decreased libido
• Alopecia (hair loss)
• Injection site reactions such as:
  • Erythema (redness)
  • Pruritus (itching)
  • Swelling
  • Rash
• Hypersensitivity reactions
• Anaphylactoid reaction (severe allergic reaction)
• Hypotension (low blood pressure)
• Arthralgia (joint pain)
• Flu-like symptoms
• Dizziness
• Abdominal pain
• Abdominal distention
• Vomiting
• Diarrhea
• Constipation
• Weight gain
• Elevated liver enzymes
• Cough
• Upper respiratory tract infection

Information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with travel medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

Generic and brand names of gonadotropin-releasing hormone antagonist drugs are:

• Antagon
• cetrorelix
• Cetrotide
• elagolix
• elagolix/estradiol/norethindrone acetate
• ganirelix
• Orgalutran
• Oriahnn
• Orilissa