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Ovulation problems

Details the use of GnRh analogues to induce ovulation including both agonists and antagonists.


Ovulation induction by GnRh analogues

These are structural modifications of the natural GnRh. GnRh analogues are often given with other drugs such as FSH to enhance ovulation stimulation for IVF cycles and prevent a spontaneous LH surge. This has been shown to decrease the cancellation rates of the treatment cycles and improve pregnancy rates. In addition, a greater control of the cycle is achieved. There are two types of GnRh analogues that are used: GnRh agonists and GnRh antagonists.

GnRh-agonists

These stimulate the GnRh receptors on the pituitary gland, resulting in an initial secretion of LH and FSH from the pituitary gland ('flare up'). However, continued treatment with GnRh-agonists leads to "damped down" down-regulation of the GnRh receptors.

Agonists are administered in the form of: nasal sprays such as synarel (nafarelin) and busereline, daily subcutaneous (under the skin) injections e.g. buserelin, intramuscular or subcutaneous depot (one depot lasts about a month) such as Zoladex (gosereline), prostap (leuprorelin) and Decapeptyl (triptorelin).

GnRh-antagonists

These occupy the GnRh receptors, but do not stimulate them. This prevents the natural GnRh from occupying and stimulating the receptors. This results in complete, immediate suppression of FSH and LH secretions. GnRh antagonist is administered by subcutaneous injections such as cetrorelix (cetrotide) and Orgalutran (Antagon). GnRH antagonists are usually given by subcutaneous injection about 4-5 days after starting stimulation with gonadotropins when high oestradiol levels may induce an LH surge. The GnRH anatgonist permits a simplified and shorter treatment cycle than GnRH agonists. The use of GnRH agonists has been shown to be associated with reduced pregnancy rates.

There are different treatment protocols for giving these medications. It should be noted that the side effects include: hot flushes, vaginal dryness, mood changes and depression.

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