Administration of GnRH analogues Administration of hCG Taking anti-oestrogens Administration of gonadotrophins
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Ovulation problems are the most frequent cause of reduced fertility. Various treatments using medication try to remedy this irregularity with the aim of inducing ovulation (ovulation-induction).Ovulation induction versus stimulation
Ovulation induction is not the same as controlled stimulation:
- in IVF|ICSI the development of several follicles at the same time is stimulated;
- in ovulation induction, hormone production is regulated to stimulate the development of usually just one follicle and to trigger a timed ovulation.
The two methods have in common that hormone preparations or anti-hormones are used.
Also, every IVF stimulation course is concluded with an hCG-injection to trigger ovulation: ovulation induction in other words.
Administering GnRH analogue
Under normal circumstances, the hypothalamus secretes a small amount of GnRH every 60-90 minutes: the gonadotrophine releasing hormone
. This hormone stimulates the hypophysis to release the sex hormones FSH and LH (gonadotrophins) which are crucial to regulate the menstrual cycle.
If the interaction between the hypothalamus and the hypophysis is disturbed due to a low frequency of GnRH release, it can be improved by the administration of synthetic GnRH.
The hormone is administered subcutaneously (under the skin).Chances of pregnancy
The (cumulative) chance of pregnancy is about 80% after six months. If after this time no pregnancy occurs, the treatment is stopped and an alternative will be sought.
Administration of hCG
Sometimes an ovulation problem is purely down to anovulation. This means that:
- the maturation process of the egg cell occurs normally: a dominant and fertile follicle is produced,
but the LH peak does not happen.
- LH is the sex hormone which suddenly increases in quantity as a result of a rise in oestrogen by the ripe follicle around the middle of the menstrual cycle, triggering ovulation after 36-42 hours.
If an ultrasound indicates a fully developed follicle (>17mm), ovulation can be triggered by administering the pregnancy hormone hCG. This has the same bioactivity as LH.
This method of ovulation induction is seldom given alone.
It is usually combined with a prior stimulation of the ovaries. This is the case in IVF treatment, where the hCG-injection is given to conclude the stimulation process.
It is administered subcutaneously (under the skin).
The use of clomiphene citrate, an anti-oestrogen, usually results in a 'natural' ovulation - and is therefore a form of ovulation induction. However, it is not a treatment in itself.
Clomiphene citrate is often used for artificial insemination and timed intercourse as a light stimulation for the ovaries.How does this anti-hormone work?
Anti-oestrogens can bind to the oestradiol receptor, which is an oestrogen.
This natural, female hormone is produced in the reproductive organs. At sufficient levels, it gives the signal to the hypophysis to release less FSH and LH (see female hormones
Anti-oestrogens intercept that signal by attaching themselves to the oestradiol receptor. The hypophysis believes there are no or insufficient levels of oestrogen. As a result, levels of FSH and LH increase, causing a light stimulation to the ovaries
If clomiphene citrate is administered after the start of menstruation (as of day three for five days), it can stimulate the simultaneous formation of a few small follicles to ripe egg cells. Via careful monitoring through blood tests and ultrasound scans, the perfect moment for ovulation can be determined and orchestrated.
Administration of gonadotrophins
During ovulation induction, gonadotrophins are sometimes used (see hormone preparations
This is done using a low dose protocol: the injected dose is adjusted so that only a light ovarian stimulation is achieved.