Lupron is a GnRH Analogue. There are many other kinds of GnRH analogues available ,such as Lupride, Buserelin, Triptorelin ( Decapeptyl) and these all act the same way. As the name suggests, they mimic the action of GnRH.
GnRH stands for Gonadotropin Releasing Hormone, which is a peptide ( a molecule which consists of a chain of amino acids) released by the hypothalamus. GnRH causes the pituitary gland to release the gonadotropin hormones, FSH ( follicle stimulating hormone) and LH ( luteinising hormone) .
These GnRH analogues have a dual mode of action. When administered, they initially stimulate the release of gonadotropins, just like GnRH dose. However, when multiple doses are given, they cause the pituitary gland to switch off , so that it no longer produces any gonadotropins. This is called downregulation. They can be administered intranasally or by injection. Brand names include Buserelin, Lupron and Lucrin.
GnRH analogs are most commonly used today as adjunctive therapy in order to enhance induction of ovulation with HMG, especially for IVF ( in vitro fertilization) treatment. Your own gonadotropins (FSH and LH) produced by your pituitary are turned off by the GnRH analogues ( this is called pituitary downregulation) , so that your physician has a clean slate to work with when administering exogenous gonadotropins to induce superovulation. Since your pituitary is switched off, the doctor can take over control of your cycle; and your ovarian follicles will now grown purely in response to the HMG injections used for superovulation in IVF. Please note that the GnRH analogues switch off only the pituitary - they have no action on the ovary itself.
GnRH analogs can be used as part of a long protocol ( when they are started on Day 21 of the pre-IVF cycle); or as part of a short protocol ( when they are started on Day 1 of the IVF cycle). We prefer the short protocol because it is easier, less expensive and ass effective.
Since the GnRH analogues switch of the production of gonadotropins, they also switch off the production of estrogen by the ovaries as well, when given over a long period of time. They thus induce a "menopausal" state, allowing the lesions of endometriosis and fibroids to shrink, since there is no further production of estrogens. In such cases, these are often used as a single short of a long-acting depot preparation ( so that multiple daily injections do not need to be given).
Interestingly, Lupron is also used for treating men with prostate cancer ! Since it switches of gonadotropin production , it stops the man's testes from producing androgens, thus reducing the man's testosterone levels and causing the pituitary tumor ( which is testosterone dependent) to shrink.