Triggering ovulation with endogenous luteinizing hormone may prevent the ovarian hyperstimulation syndrome.

In a series of 126 therapeutic cycles in 48 patients with primary infertility and treated with HMG for anovulation or preparation to insemination, ovulation was triggered by endogenous LH instead of HCG when the patient was considered to be at high risk for ovarian hyperstimulation syndrome (OHS), (plasma oestradiol greater than 1200 pg/ml) and/or multiple pregnancy (greater than 3 follicles greater than 17 mm in diameter). The endogenous LH surge was provoked and maintained by intranasal buserelin 200 micrograms three times at 8-hourly intervals. In the 37 cycles with buserelin, no OHS occurred despite high preovulatory levels of oestradiol; a single twin pregnancy was recorded despite the presence of numerous mature preovulatory follicles. Conception results (21.6% pregnancy per therapeutic cycle) compared favourably with HCG administration (16.8%). It is concluded that, when ovulation must be triggered in a hazardous situation, the use of endogenous LH through the administration of a short-acting GnRH analogue prevents the complications of exaggerated follicular stimulation.