In order to obtain a workable number of eggs for in-vitro fertilization (IVF) the ovary must be stimulated with gonadotrophins (follicle stimulating hormone- FSH). Without this stimulation, only one egg is obtainable every month and this is not usually enough to produce a good embryo for placement in the uterus. Multiple eggs provide a better chance that at least one good embryo will be produced following fertilization by the sperm.
During this stimulation of the ovaries to produce a number of ovulations, several problems may be encountered. Too little stimulation will not produce the ideal number of eggs and overstimulation with doses that are too large may be disastrous. While these are dependent on the doctor, the internal production of hormones may interfere with the smooth process of stimulation of ovulation. The main culprit is luteinizing hormone (LH) produced by the pituitary gland. High levels of LH can seriously affect the quality of the eggs produced and even halt the process completely. In order to suppress the production of LH during stimulation the pituitary gland must be prevented from its normal response to rising levels of estrogens in producing LH. One of the ways to do this is with gonadotrophin releasing hormone (GnRH) agonist. These injections are very efficient at shutting down the production of LH within a couple of days. Although they produce a short initial rise in the levels of LH, the production of this hormone is then completely suppressed.
The commonest way of giving the GnRH agonist is the so-called long protocol. The injections are started on day 21 of the cycle preceding the treatment cycle and continued right up to the time that the stimulation is halted and the ovulation triggered. This ensures that virtually no LH is produced and that stimulation of ovulation starts and continues in the presence of a level playing field where only the given hormones have a say. The treating physician thus has control of the hormonal events. This also has the advantage of allowing some flexibility in the timing of egg collection as the interfering factors are suppressed.
Treatment with GnRH agonist in a long protocol may produce symptoms similar to those of the menopause but once stimulation of the ovaries is started, usually after about 10 days of GnRH injections, these symptoms stop. GnRH agonist may also be given in the form of a nasal spray and many find this way of administration more convenient. The long protocol is just that, long, and although it is very efficient, prolongs the overall time of treatment. Further, relatively large quantities of FSH for stimulation are needed compared with other protocols. Despite these disadvantages, the use of the long protocol of GnRH agonist has consistently produced the best results from IVF treatment.