Abstract: During a spontaneous menstrual cycle, a preovulatory luteinizing hormone （LH） surge initiates the complex ovulatory process whereby an oocyte is released from the ovarian follicle. As the result of LH surge, the oocytes complete meiosis I and enter meiosis II, the cumulus-oocyte complex separates from the follicle wall, and the process resulting in the release of the oocyte-cumulus complex is started. Human chorionic gonadotrophin （ｈＣＧ） was usually used as a surrogate ＬＨ surge to induce the final ovarian maturation in assisted reproductive technology （ＡＲＴ）, because hCG induces the necessary changes through the LH receptor. But the molecular mechanisms of oocyte maturation induced by LH surge in natural cycle are still unclear. The content of LH receptor on granulosa cell increases with the growth of follicles, and reaches a peak before the maturity of follicles, which make the growing follicles to be ready for the response to LH surge. High LH surge acts on GCs by its receptors, stimulating type G protein/adenosine cyclase/cAMP/cAMP-dependent protein kinase （Gs/AC/cAMP/PKA） pathway to increase intracellular cAMP concentration. The activated transcription factors, including cAMP response element binding protein 1 （ＣＲＥＢ１） ａnd cAMP-response element modulator （ＣＲＥＭ）, causes the activation or inhibition of some gene expressions which related on oocytes maturation and ovulation. All these result in the ovulation and the formation of corpus luteum.

Key words: Luteinizing hormone, Receptors, LH, Ovulation, Reproductive techniques, assisted, Chorionic gonadotropin