GnRH agonists
GnRH agonists can be prescribed for a number of different reasons including the treatment of endometriosis and fibroids. This section however concentrates on the use of GnRH agonists in fertility treatments, especially assisted reproduction techniques.
Ironically, the naturally occurring hormones (oestrogen, androgen and gonadotropins) that are so important for fertility can themselves interfere with fertility treatments. As a result during in vitro fertilisation (IVF) and associated procedures, it is important to avoid the possibility of a premature (spontaneous) ovulation resulting in the loss of the ova (egg) needed for the IVF treatment.
To avoid premature ovulation, your own hormonal factory is therefore suppressed or shut down during hormonal stimulation. This can be achieved with the administration of GnRH agonists An agonist is a drug that mimics a naturally occurring hormone. GnRH agonists halt the natural hormonal activity of a woman so that the gonadotropin treatment can run as appropriately as possible. They are administered by injection.
The newer GnRH antagonists also prevent premature ovulation in a more direct manner.
how they work
GnRH agonists mimic the effects of natural GnRH. At first, they stimulate the pituitary gland to produce FSH and LH (the so-called flare-up effect). However, with continued use, they lead to a suppression of these hormones, due to exhaustion and tolerance of the pituitary (This is referred to as a down-regulation.) The second part of their actions – that is the suppression of FSH and LH – is the one that is important. Natural ovulation is stimulated by a rise of LH (LH peak) so suppressing natural LH production minimises the chance of a premature ovulation.
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possible side effects
- Local reaction where the injection took place.
- Headache, nausea, dizziness, depression, allergic reactions.
- Loss of bone density (if used for long periods).
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