促性腺激素峰的作用与人绒毛膜促性腺激素诱发排卵

Role of gonadotropin surge and hCG triggering ovulation

黄体生成素（LH）峰是即将排卵的可靠指标，出现于卵泡破裂前34～36h，通常持续48～50h，LH阈值必须维持14～27h，才可确保排卵前卵泡的最后完全成熟。促性腺激素（Gn）峰对卵细胞最后成熟、孕酮的合成、排卵、黄体形成等一系列复杂的生理过程都是至关重要的。LH峰出现到排卵前卵泡发生了显著的变化。诱发排卵前颗粒细胞和卵母细胞发生许多关键变化，如抑制颗粒细胞增殖基因的转录、丢失缝隙连接、诱导排卵所需要的基因如环氧合酶2等。

Gonadotrophin surge is a key event to improve oocyte final maturation and induce ovulation. There are a series of complicated physiological changes in follicles and oocytes during luteinizing hormone （LH） surge and ovulation, such as resumption of oocyte meiosis, cumulus cells dispersion, expansion and mucification, and then separation from follicle wall in favour of ovulation, luteinization of granular and theca cells, and upregulation of growth factor such as VEGF-A, FGF2 and the important cytokines related to normal implantation and prophase neovascularization. The surge triggered by hCG or GnRH agonist（GnRH-a） in ovulation induction is different from normal LH surge. The half life of hCG is long, with a strong affinity to LH receptor, so ovarian hyperstimulation syndrome （OHSS） easily happens.. In addition, hCG only has LH effect and no FSH effect. The gonadotrophin surge triggered by GnRH-a includes both FSH and LH effects, but it is easy to result in luteal phase defect, embryonic implantation failure, and reduction in pregnancy rate due to the effect of short duration. Modified luteal phase support could significantly improve the pregnancy rate.