In women, ovulation disturbances are the most frequent causes of infertility: the hormonal exchanges between the brain and reproductive organs are imbalanced. Various treatments attempt to correct the imbalance, with the triggering of ovulation as the goal (ovulation induction).

Induction of ovulation is not the same as controlled ovarian stimulation: in ovarian stimulation (or super ovulation) the development of follicles is stimulated; in induction of ovulation 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 the fact that hormone preparations or anti hormones are used in both. Additionally, every IVF stimulation course is concluded with a timed triggering of ovulation, via the administration of hCG injection.

Under normal circumstances, the hypothalamus secretes a small amount of GnRH (gonadatrophin releasing hormone) every 60-90 minutes.. This in turn stimulates the hypofyse to release the sex hormones FSH and LH (gonadotrophins). These two hormones are crucial to the regulation of the menstrual cycle.

If the exchange between the hypothalamus and the hypofyse 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.

chance of pregnancy
The (cumulative) chance of pregnancy is about 80% after six months. If after this time no pregnancy occurs, the treatment is stopped an an alternative will be sought.

   

Sometimes an ovulation problem is purely down to anovulation. This means that the maturation process of the egg cell occurs normally and a follicle is produced, but the LH peak does not happen. LH is the 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 via the administration of  the pregnancy hormone hCG. This has the same bioactivity as LH. The injection has te be given subcutaneously. 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.

 

    

Even though the administration of clomifeen citrate, an anti-oestrogen, leads to a natural ovulation and therefore is a form of ovulation induction, it is not a treatment in itself. Clomifeen citrate is often used for artificial insemination and timed intercourse as a light stimulation for the ovaries.

Anti-oestrogens can bind to the receptors of oestrogens, or in other words, to the naturally occurring hormones which are produced in the reproductive organs of a woman and which at sufficient levels, give the signal to the hypofyse to release less FSH and LH (see female hormones).
Anti-oestrogens intercept that signal by attaching themselves to the oestrogen receptors, which provides the impression that there insufficient levels of oestrogen in the system. As a result, levels of FSH ans LH increase, causing a light stimulation to the ovaries.
If clomifeen 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. 

    

During ovulation induction, gonadotrophines are sometimes made use of (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.