The Gonadotropin Surge in Human Reproduction: Endocrine and Biochemical Mechanisms

Hh, Goh

doi:10.1016/s0065-2423(08)60335-2

Cited by 4 publications

(4 citation statements)

References 149 publications

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“…A timely LH surge of adequate amplitude and sufficient duration is important to bring about rapid and complex cellular differentiation, resulting in cascades of tightly coupled biochemical events, which initiate oocyte maturation, ovulation, and corpus luteum formation (Goh, 1994). Bomsel-Helmreich et al (1989) have demonstrated that the induction of ovulation required a higher hCG dose than oocyte maturation; therefore, a failure to ovulate at a lower hCG dose may not imply the presence of a defective biochemical or cellular mechanism for ovulation.…”

Section: Discussionmentioning

confidence: 99%

“…Higher incidence of oocyte aneuploidy in hamster (Hansmann et al, 1988), meiotically abnormal oocytes in rats (Yun et al, 1989) and overmature oocytes in sheep (Moor et al, 1985) were noted following hyperstimulation with exogenous gonadotrophins. It is known that a midcycle luteinizing hormone (LH) surge of sufficiently high amplitude and duration is important for both nuclear and cytoplasmic maturation, which ensure the normal fertilization and developing potential of oocytes (Goh, 1994). Following the maturational process, mature oocytes, which are ovulated, are arrested at metaphase II in the haploid stage.…”

Section: Introductionmentioning

confidence: 99%

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Effects of hyperstimulation with gonadotrophins and age of females on oocytes and their metaphase II status in rats

Tain

Goh

2000

Mol. Reprod. Dev.

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The present study was undertaken to evaluate the effects of hyperstimulation and aging on the number and proportion of oocytes in the metaphase II stage in female Wistar rats. It explored the validity of the hypothesis that a combination of hyperstimulation with pregnant mare serum gonadotrophins (PMSG) and age could compromise, to a greater extent, the oocyte quality as indicated by the proportion of ovulated oocytes in the metaphase II stage. Female Wistar rats were stimulated with varying doses of PMSG and human chorionic gonadotrophins (hCG) and the number and proportion of ovulated oocytes in the metaphase II stage were examined and compared between different groups of young adult (8–10 weeks old) and aging (30–32 weeks old) female rats. While spontaneous ovulation occurred in all young adult rats, only 50% of the aging rats did. The ovulation rate in aging rats was increased from 50 to 93% when non‐PMSG‐stimulated rats were given a dose of 10 IU of hCG at proestrus. The lower number of ovulated oocytes noted, even in those hyperstimulated with high doses of PMSG/hCG, also indicated a reduction in fertility in aging rats. Under the influence of high doses of PMSG, all aging rats ovulated, but as with the young adult rats, a higher dose of hCG was needed to achieve the maximum number of ovulated oocytes from the PMSG‐induced expanded pool of preovulatory follicles. However, the average number of ovulated oocytes in aging rats was, nevertheless, still significantly lower than in young adult rats even when approximation of weight was considered. No consistent significant difference in proportion of normal oocytes was noted within groups and between young adult and aging rats. A lower proportion of ovulated oocytes was arrested at the metaphase II stages when rats, whether they were young adult or aging, were hyperstimulated with 40 IU of PMSG. However, this proportion was restored to normal (about 100%) when a higher dose of hCG, which is a signal responsible for initiating oocyte maturation, was used. Results of the present study showed that there appears to be an age‐related reduction of sensitivity of the preovulatory follicles to the ovulation induction signal of hCG and thus higher doses of hCG were needed to ovulate the PMSG‐induced expanded pool of dominant follicles. In older rats, apart from the obvious depletion of the pool of follicles, the evidence from the present study suggests that some of these older rats do have follicles, but that these were unable to develop to preovulatory follicles, probably because of the absence of sufficiently high levels of gonadotrophins essential for the initiation of folliculogenesis. PMSG‐hyperstimulation can affect nuclear maturation; the proportion of ovulated oocytes not arrested at the metaphase II stage was higher. However, the proportion of ovulated oocytes at the metaphase II was restored to normal by increasing the dose of hCG use. Hence, meiotic aberration in rats is not age‐dependent but rather dependent on the amplitude of the luteinizing hormone...

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of hyperstimulation with gonadotrophins and age of females on oocytes and their metaphase II status in rats

Tain

Goh

2000

Mol. Reprod. Dev.

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“…A timely LH surge of adequate amplitude and sufficient duration is important to bring about rapid and complex cellular differentiation, resulting in cascades of tightly coupled biochemical events, which initiate oocyte maturation, ovulation, and corpus luteum formation [199]. It is known that a midcycle LH surge of sufficiently high amplitude and duration is important for both nuclear and cytoplasmic maturation, which ensure the normal fertilization and developing potential of oocytes [199].…”

Section: Part Onementioning

confidence: 99%

“…It is known that a midcycle LH surge of sufficiently high amplitude and duration is important for both nuclear and cytoplasmic maturation, which ensure the normal fertilization and developing potential of oocytes [199]. For PMSG-hyperstimulated rats, higher doses of hCG are required to completely ovulate the expanded cohort of preovulatory follicles [200].…”

Section: Part Onementioning

confidence: 99%

The role of aromatase inhibitors in ameliorating deleterious effects of ovarian stimulation on outcome of infertility treatment

Mitwally

Casper

Diamond

2005

Reprod Biol Endocrinol

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Clinical utilization of ovulation stimulation to facilitate the ability of a couple to conceive has not only provided a valuable therapeutic approach, but has also yielded extensive information on the physiology of ovarian follicular recruitment, endometrial receptivity and early embryo competency. One of the consequences of the use of fertility enhancing agents for ovarian stimulation has been the creation of a hyperestrogenic state, which may influence each of these parameters. Use of aromatase inhibitors reduces hyperestrogenism inevitably attained during ovarian stimulation. In addition, the adjunct use of aromatase inhibitors during ovarian stimulation reduces amount of gonadotropins required for optimum stimulation. The unique approach of reducing hyperestrogenism, as well as lowering amount of gonadotropins without affecting the number of mature ovarian follicles is an exciting strategy that could result in improvement in the treatment outcome by ameliorating the deleterious effects of the ovarian stimulation on follicular development, endometrial receptivity, as well as oocyte and embryo quality. PART ONE IntroductionCurrent epidemiological evidence suggests that 15% of couples will experience infertility. Background prevalence rates now appear to be reasonably stable, but there is evidence of an increase in the rate of referrals for medical help [1,2]. Farley and Belsey, 1988 [3], have reported estimates of the prevalence (percentage) of primary infertility by region and country.

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Association of molecular variants of luteinizing hormone with menstrual disorders

Ramanujam

Liao

Roy

et al. 1999

Clinical Endocrinology

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The Gonadotropin Surge in Human Reproduction: Endocrine and Biochemical Mechanisms

Cited by 4 publications

References 149 publications

Effects of hyperstimulation with gonadotrophins and age of females on oocytes and their metaphase II status in rats

Effects of hyperstimulation with gonadotrophins and age of females on oocytes and their metaphase II status in rats

The role of aromatase inhibitors in ameliorating deleterious effects of ovarian stimulation on outcome of infertility treatment

Association of molecular variants of luteinizing hormone with menstrual disorders

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