Ovulation induction by pulsatile GnRh (gonadotropin releasing hormone)
The hypothalamus gland secretes GnRh (gonadotropin releasing hormone) in a pulsatile fashion (in small amounts every hour or so) to stimulate the pituitary gland to secrete FSH and LH. This in turn induces follicular development. Commercial GnRh preparations are produced synthetically e.g. Fertiral can be given to a patient subcutaneously (underneath the skin) via a programmable infusion pump that can be worn day and night without discomfort; it gives intermittent doses of GnRh for several days. Monitoring of treatment is usually carried out by ultrasound scanning.
Synthetic GnRh can be given in selected cases instead of hMG or FSH e.g. patients who have polycystic ovarian syndrome and did not respond to other drugs, and in those patients who do not ovulate and have hypothalmic failure.
Synthetic GnRh is an effective drug (over 90% of cycles are ovulatory and a pregnancy rate of about 80-90% after 6 months). In contrast to FSH and hMG, it usually stimulates only one follicle to grow and so the risk of multiple pregnancy and ovarian hyperstimulation syndrome are lower.
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