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Synthetic GnRH stimulates the pituitary gland to secrete LH and FSH. It is used to induce ovulation in selected women with hypothalamic dysfunction. The hormone has to be given in a manner which mimics the natural secretion of LHRH, i.e. in "pulses" approximately 90 minutes apart. This is given by means of a small pump placed under the skin of the arm or abdomen. This treatment is now given instead of HMG at certain specialist centres. It has the advantage over HMG that it produces an ovulation cycle which is similar to the natural cycle and multiple ovulation is very unusual.
These drugs may be used for the treatment of endometriosis and fibroids. They work by initially stimulating, then switching off (down-regulating) the pituitary gland, and are administered intranasally or by injection. They thus induce a "menopausal" state, allowing the endometriosis and fibroids to shrink, since there is no further production of estrogens.
GnRH analogues are most commonly used today as adjunctive therapy in order to provide better control of superovulation with HMG, especially for IVF (in vitro fertilisation) treatment. Your own gonadotropins (FSH and LH) 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.
Currently, most in vitro fertilization (IVF) centres use pituitary down-regulation with gonadotrophin-releasing hormone (GnRH) agonists to prevent premature luteinization. However, this requires at least 7-14 days of GnRH agonist pretreatment. A more rational approach would be to use the newer GnRH antagonists, which cause an immediate blockage of the GnRH receptors on the pituitary gland. Thus, treatment with the antagonist can be limited to only those 2-3 days when high oestradiol levels may induce an LH surge. Clinical experience with GnRH antagonists in IVF treatment thus far has been encouraging and demonstrates a high efficacy in preventing the LH surge.
Some women will respond very poorly to HMG injections. They grow few or no follicles, in spite of being given large doses. In some of these "poor responders" synthetic growth hormone (HGH, human growth hormone) has been used to try to enhance the response of the ovary to the HMG. However, the response to this very expensive drug has been quite disappointing, and it is very infrequently used.
© Dr. Aniruddha Malpani and Dr. Anjali Malpani www.drmalpani.com
Credits: How to Have a Baby: Overcoming Infertility
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