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Gonadotropin-Releasing Hormone Analogs (GnRHa)
Analogs are chemicals that have similar shapes, but not necessarily similar functions. GnRH analogs are drugs that are structurally similar to a natural hormone known as gonadotropin-releasing hormone (GnRH). Usually, GnRH (sometimes called luteinizing hormone-releasing hormone, LHRH) promotes the secretion of follicle stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary gland.
GnRH antagonists (blockers), such as cetrorelix and ganirelix, keep the pituitary from making LH. Approved by the FDA for treating infertility in women, they are rarely used to treat male infertility.
GnRH agonists (promoters), such as leuprolide, trick the pituitary gland into making too much FSH and LH. Very high levels of those hormones then cause the pituitary to stop making any more. GnRH agonists are used to treat breast cancer, endometriosis, and prostate cancer. They may also help to protect fertility for individuals who are undergoing cancer treatments that may damage the testicles or ovaries. Although GnRH agonists are not FDA-approved for treating infertility, they are used for both male and female infertility. In men, they may be used occasionally to help increase the production of sperm. More often, GnRH agonists are given to women in combination with other fertility drugs because they improve the predictability of ovulation.
For women, both types of GnRH analogs stop ovulation. Then, the woman takes an ovulation inducing (stimulating) drug so she will ovulate at an accurately-determined time. Egg-collecting or artificial insemination procedures can be performed at the best times for good results.
Drugs in the class
Leuprolide (Eligard, Lupron)
Goserelin (Zoladex) | 
