王美仙,邵小光
人绒毛膜促性腺激素日孕酮升高对体外受精的影响
王美仙,邵小光△
【摘要】控制性卵巢刺激(controlled ovarian stimulation,COS)中,人绒毛膜促性腺激素(hCG)日孕激素升高时有发生。由于界定值不同,发生率报道亦不同。孕酮水平与成熟卵泡数目、雌二醇水平和总卵泡刺激素(FSH)剂量正相关。过早的孕酮升高可以改变子宫内膜基因表达,加速子宫内膜成熟,促使子宫内膜由分泌早期向分泌中期转变,导致子宫内膜和胚胎发育不同步,影响子宫内膜容受性。hCG日孕酮升高降低体外受精周期的种植率和活产率。选用温和的COS方案、减少FSH剂量、提前hCG诱发排卵时间、全胚冷冻后解冻移植、囊胚移植等方法可以避免孕酮升高导致的不利影响。
【关键词】绒毛膜促性腺激素;孕酮;超排卵;受精,体外;妊娠率
△审校者
(J Int Reprod Health/Fam Plan,2016,35:142-145,150)
自然月经周期中,从卵泡中期开始由单个卵泡分泌孕酮,且此时循环中的卵泡刺激素(FSH)浓度开始下降,所以孕酮浓度很低,为1.59~3.17 nmol/L。在黄体生成激素(LH)峰日,孕酮轻度升高协同雌激素的正反馈效应,诱发排卵。在控制性卵巢刺激(controlled ovarian stimulation,COS)过程中,能观察到人绒毛膜促性腺激素(hCG)注射前血清孕酮提前轻度升高现象,与颗粒细胞过早黄素化不同的是LH并未升高,但常伴随着多卵泡和高雌激素。这种孕酮升高不影响卵子质量,只影响子宫内膜容受性。综述hCG日孕酮升高的界定及其对体外受精(IVF)的影响。
Schoolcraft等[1]于1991年首先报道了部分人群在促性腺激素释放激素激动剂(GnRHa)降调节的IVF周期中,hCG日孕酮升高现象。孕酮升高的发生率目前报道不一,其发生率的不同可能与界定值不同有关。最初的报道中孕酮升高的界定值是0.8~2.0 ng/mL[2-6]。孕酮升高发生率在GnRHa周期中可高达35%,而GnRH拮抗剂(GnRHA)周期中可高达38%[6-7],但是这个结论有些武断。2010年Bosch等[8]回顾性分析4 000 个GnRHa和GnRHA周期,孕酮升高界定为1.5 ng/mL,发生率为8.5%。2011年VanVaerenbergh等[9]用新的方法也将孕酮升高界定为1.5 ng/mL,并被很多学者支持和使用。近年随着研究的深入,目前对于孕酮升高的界定仍报道不一,应用的研究方法并不一致。有研究分析了2 566个周期,长方案中孕酮升高(孕酮>1.2 ng/mL)的发生率是22.86%,短方案中孕酮升高(孕酮>2.0 ng/mL)的发生率是27.63%[10]。Xu等[11]分析了11 055个新鲜周期和4 021个解冻移植周期,按照卵巢反应性不同界定了孕酮升高的不同界值,卵巢低反应的孕酮升高界定为1.5 ng/mL,卵巢反应正常的孕酮升高界定为1.75 ng/mL,卵巢高反应的孕酮升高界定为2.25 ng/mL。
在COS中,血清孕酮是晚卵泡期所有优势卵泡分泌孕酮的总和[12]。孕酮水平与成熟卵泡数目和雌二醇(E2)水平呈正相关。有Meta分析证实孕酮升高与hCG日E2高水平和卵泡数目多有关[13-14]。过量的外源性促性腺激素作用于颗粒细胞,促使胆固醇向孕酮转化[8]。GnRHa长方案中用高纯度尿源性人绝经期促性腺激素(HP-HMG)促排卵的孕酮升高发生率是6.3%,而FSH促排卵孕酮升高的发生率是13.8%,提示孕酮升高与FSH用量呈正相关[15]。根据两种细胞-两种促性腺激素理论,在卵泡膜细胞通过LH的作用使孕酮转化成雄激素,然后在卵泡颗粒细胞通过FSH诱导的芳香化酶作用再将雄激素转化成雌激素。在卵泡颗粒细胞黄素化之前,LH通过增加孕酮向雄激素的转化来减少循环中孕酮水平。因此,如果垂体降调节抑制过深,LH活性相对不足,给予大剂量的FSH刺激获得的多卵泡所产生的孕酮就会明显升高。此外,COS中添加LH时机不同也可能会导致孕酮升高[16]。
从20世纪90年代开始关于孕酮升高对IVF结局影响的争论不一,2007年Venetis等[13]对发表过的文献做了Meta分析,试图解决这一问题。其得出的结论是hCG日孕酮升高者临床妊娠率低,但与孕酮未升高者比较差异无统计学意义,不能说明孕酮升高对IVF妊娠结局有不良影响。但2008年de Ziegler等[17]对Venetis的统计学方法提出了质疑。2011年与Venetis同一团队的Kolibianakis等[14]对拮抗剂周期进行了Meta分析,认为hCG日孕酮升高降低临床妊娠率。Bosch 等[8]也得出类似结论,把孕酮升高界定为1.5 ng/mL,认为hCG日孕酮升高可以降低继续妊娠率。随后的研究虽然孕酮升高的界定值不统一,但结论大多是孕酮升高影响IVF结局。Xu等[11]研究显示,不管卵巢反应性如何,hCG日孕酮升高降低了着床率和继续妊娠率。2013年Venetis等[18]对60 000个周期进行了Meta分析,认为hCG日孕酮升高降低GnRHa或GnRHA方案新鲜移植周期妊娠率,国内研究也证实孕酮升高降低了卵裂期胚胎移植妊娠率[19-20]。
有研究发现,在1 719个长方案(孕酮<1.2 ng/mL者为40.65%,孕酮>1.2 ng/mL者为29.77%)和847个短方案(孕酮<2.0ng/mL者为30.18%,孕酮>2.0 ng/mL者为23.50%)的新鲜移植周期中,孕酮升高者的活产率均降低。而长方案(孕酮<1.2 ng/mL者为29.31%,孕酮>1.2 ng/mL者为25.35%)和短方案(孕酮<2.0 ng/mL者为24.84%,孕酮>2.0 ng/mL者为24.22%)的解冻移植周期中活产率无明显差异。Hill等[21]分析了934个囊胚期移植周期和686个卵裂期移植周期,提示对于预后较好的IVF患者,孕酮升高不影响获卵率、受精率、优质胚胎率,但活产率降低(孕酮<1.5 ng/mL者为49.7%,孕酮>1.5 ng/mL者为24.5%,P=0.001)。Ochsenkühn等[22]分析了2 555个新鲜移植周期,按hCG日孕酮水平分为3组,分别为<1.5 ng/mL、1.5~1.99 ng/mL、≥2.0 ng/mL,3组的活产率分别为24.6%、26.7%和17.4%,再次证实孕酮升高对活产率有不利影响。
尽管近年研究证实孕酮升高对IVF结局有负面影响,但其中的内分泌机制仍不清楚。多数研究认为孕激素对卵子、胚胎质量没有影响,是由于降低子宫内膜容受性而影响了IVF结局[4,23-24]。已有研究均证实孕酮升高降低新鲜移植周期的妊娠率,而不影响解冻移植周期的妊娠率[10,18],因此认为孕酮升高通过影响子宫内膜容受性而降低妊娠率。有学者推测其原因是孕酮升高可影响子宫内膜的成熟,导致子宫内膜和胚胎发育不同步[25]。另有学者证实子宫内膜和胚胎发育不同步超过3 d即不可能妊娠[26-27]。而过早的孕酮升高可以改变子宫内膜基因表达,加速子宫内膜成熟,促使子宫内膜由分泌早期向分泌中期转变,导致子宫内膜和胚胎发育不同步,影响子宫内膜容受性[28]。
近年有学者开始用基因芯片研究孕酮升高对子宫内膜基因表达谱的影响。2011年Van Vaerenbergh等[9]对GnRHA、基因重组FSH刺激周期的IVF患者在取卵日进行内膜活检并检测内膜基因表达,按照hCG日孕酮水平分为<2.86 nmol/L、2.86~4.77 nmol/L、>4.77 nmol/L 3组,3组的E2水平、获卵数差异无统计学意义,<2.86 nmol/L和2.86~4.77 nmol/L两组间基因表达的差异是小的(5个上调和23个下调),2.86~4.77 nmol/L和>4.77 nmol/L两组之间的基因表达的差异是大的(607个上调和212个下调),说明hCG日不同孕激素水平的子宫内膜的基因表达不一,证实了孕酮升高可影响子宫内膜容受性。2011年Labarta等[29]用基因芯片研究了捐卵者的子宫内膜的基因表达,选择在hCG日后第7天进行子宫内膜活检,发现孕酮<1.5 ng/mL和>1.5 ng/mL基因表达明显不同,而基因表达改变与细胞黏附、发育过程、免疫系统有关,会影响胚胎在子宫内膜的着床过程。
但也有文献证实子宫内膜能够在超生理状态的雌激素下恢复与胚胎的同步性,孕酮升高只是加速分泌早期的子宫内膜成熟,并没有影响到整个种植期。特别是GnRHA周期,孕酮升高只影响卵裂期胚胎移植的临床结果,而不影响囊胚期胚胎移植的临床结果[23]。
目前多数研究报道hCG日孕酮升高对IVF受精率是没有影响的。Santos-Ribeiro等[15]的报道中不同的孕酮水平(≤0.50 ng/mL,0.50~1.5 ng/mL,>1.50 ng/mL)之间的IVF受精率是相似的,分别为74.4%、73.3%和75.6%,证实hCG日孕酮升高不影响IVF受精率,与Kyrou等[30]的报道一致。但2014年Huang等[31]研究了9 858个IVF周期,补救行胞浆内单精子注射(ICSI)的发生率是6.98%(688/9 858),补救ICSI周期hCG日平均孕酮为1.38 ng/mL,明显高于9 170个IVF周期的孕酮值(1.29 ng/mL),而两者的妊娠率差异无统计学意义(43.5% vs. 41.6%,P>0.05)。该研究认为hCG日孕酮升高可降低IVF受精率,使得补救ICSI概率增加。此外还确定了孕酮升高的界定值为1.5 ng/mL,>1.5 ng/mL患者的补救ICSI概率明显增加。并且推测由于孕酮升高导致卵子提前成熟或卵子老化,进而影响受精率。因此,hCG日孕酮升高是否对受精率有负面影响尚需进一步研究。
COS中如何尽量避免高危人群发生孕酮升高,学者们做了很多研究。2014年Werner等[32]研究认为COS中外源性促性腺激素用量比例即LH/FSH在0.3~0.6之间者hCG日孕酮>1.5 ng/mL比率最低,为20%,而外源性LH/FSH<0.3和>0.6者hCG日孕酮升高发生概率较高,分别为32%和23%,可以通过调整人绝经期促性腺激素(HMG)/基因重组LH和FSH的用药比例而降低孕酮升高的发生率。温和的COS可以降低E2水平进而有效降低hCG日孕酮升高的比例[30]。适当提前hCG诱发排卵可以避免孕酮升高,当3个或3个以上卵泡直径>16 mm时即给予hCG诱发排卵,不会影响妊娠率[33],但可能导致不成熟卵泡比例上升。全胚胎冷冻后自然周期解冻移植也可以避免孕酮升高的不利影响。有学者提出新鲜周期囊胚期胚胎移植可避免hCG日孕酮升高带来的不利影响[34],但也有学者提出不同意见,认为孕酮升高者囊胚期胚胎移植妊娠率仍明显降低[35]。因此,囊胚移植能否避免孕酮升高带来的负面影响尚需进一步研究。
目前引起孕酮升高的机制报道很多,主要与超促排卵的高E2水平和成熟卵泡数目多、大剂量FSH和低LH有关。孕酮升高主要影响子宫内膜容受性而降低妊娠率和活产率。通过改变或避免这些因素可以指导临床医生优化促排卵方案或移植方案,尽可能改善生化及临床妊娠结局。孕酮升高的发生率报道不一,界定值亦无统一标准,可能与各个中心不同的实验方法有关。不同的促排卵方案、不同的卵巢反应性,其孕酮升高的阈值可能也不同,仍需要进行多中心、大样本研究。孕酮升高对IVF受精及卵泡微环境的影响需要进一步研究。而是否能够在促排卵前预测孕酮升高,并做恰当的预处理也值得进一步研究。虽然有学者提出基础孕酮>0.45 ng/mL 是hCG日孕酮升高的高危因素,但是样本量少,尚需大样本研究证实[36]。
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·综述·
Increased Level of Progesterone on the Day of hCG to the Disadvantage of IVF Outcomes
WANG Meixian,SHAO Xiao -guang. Dalian Municipal Women and Children′s Medical Center,Dalian Reproductive and Genetic Medicine Center,Dalian 116000,Liaoning Province,China
【Abstract】During controlled ovarian stimulation (COS), the concentration of serum progesterone sometimes increases on the day of human chorionic gonadotropin (hCG) administration. The occurrence rate of increased progesterone level was different, due to the different cutoff value based on some publications. The progesterone concentration is positively related to the number of mature follicles, the estradiol level and the total administration dose of follicle-stimulating hormone(FSH). The premature progesterone elevation could change endometrial gene expression, accelerate endometrial maturation, and affect endometrium from early- to mid-secretory phase, which result in the developmental asynchronism between endometrium and embryo, and affect the endometrial receptivity. The progesterone elevation on the day of hCG is negatively related to the implantation rate and the rate of live birth in IVF. Those negative effects of progesterone elevation can be avoided by the moderate COS protocol, the low dose of FSH, the earlier administration of hCG, the frozen-thawed embryo transfer, and the blastocyst embryo transfer.
【Keywords】Chorionic gonadotropin;Progesterone;Superovulation;Fertilization in vitro;Pregnancy rate
作者单位:116000大连市妇女儿童医疗中心,大连市生殖与遗传医学中心