Influence of corpus luteum age on the steroidogenic response to exogenous human chorionic gonadotropin in normal cycling women

Evaluation of endometrial receptivity and implantation failure

PURPOSE OF REVIEW

To succinctly review the basic mechanisms of implantation and luteal phase endometrial differentiation, the etiologies of impaired endometrial function and receptivity, and the current methods that exist to evaluate and treat impaired endometrial receptivity.

RECENT FINDINGS

Human embryo implantation requires bidirectional communication between blastocyst and a receptive endometrium. Etiologies of impaired endometrial receptivity are varied. Some of these include delayed endometrial maturation, structural abnormalities, inflammation, and progesterone resistance. Current methods to evaluate endometrial receptivity include ultrasonography, hysteroscopy, and endometrial biopsy. Treatments are limited, but include operative hysteroscopy, treatment of endometriosis, and personalized timing of embryo transfer.

SUMMARY

Although some mechanisms of impaired endometrial receptivity are well understood, treatment options remain limited. Future efforts should be directed towards developing interventions targeted towards the known mediators of impaired endometrial receptivity.

Independent serum markers of corpora lutea function after gonadotropin-releasing hormone agonist trigger and adjuvant low dose human chorionic gonadotropin in in vitro fertilization

OBJECTIVE

To characterize corpora lutea (CL) function after gonadotropin-releasing hormone agonist (GnRHa) trigger with the use of adjuvant human chorionic gonadotropin (hCG).

DESIGN

Secondary analysis of serum from prospective randomized clinical trial.

SETTING

University-based fertility center.

PATIENT(S)

Women under 40 years of age at risk of ovarian hyperstimulation syndrome (OHSS) with serum E₂ level <4,000 pg/mL.

INTERVENTIONS(S)

All subjects underwent ovarian stimulation with the use of a GnRH antagonist protocol. Within a larger study, subjects were randomized to receive 1,000 IU hCG at the time of GnRHa trigger and placebo at the time of vaginal oocyte retrieval (VOR) or placebo at the time of GnRHa trigger and 1,500 IU hCG at the time of VOR.

MAIN OUTCOME MEASURE(S)

Luteal phase and early pregnancy curves of serum prorenin and 17α-hydroxyprogesterone (17OH-P).

RESULT(S)

Thirty subjects enrolled in this secondary analysis. Serum 17OH-P peaked in the early luteal phase, 5 days after GnRHa trigger, with a nadir in the mid-luteal phase 9 days after trigger. Serum prorenin peaked in the luteal phase 2 days after GnRHa trigger, independently from adjuvant hCG timing, and reached a nadir at 9 days after trigger. CL function appears higher when adjuvant hCG is given at VOR compared with adjuvant hCG given at the time of trigger.

CONCLUSION(S)

CL function, as interpreted by proxy measures of serum prorenin and 17OH-P with pregnancy, continues despite GnRHa trigger. Both options for adjuvant hCG timing are sufficient for CL rescue and successful pregnancy, so the potential for OHSS risk with increased CL activity after hCG at VOR should be considered.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01815138.

A randomized double-blinded controlled trial of hCG as luteal phase support in natural cycle frozen embryo transfer

STUDY QUESTION

Does the use of hCG as luteal phase support in natural cycle frozen embryo transfer (FET) increase the ongoing pregnancy rate?

STUDY ANSWER

The use of hCG in natural cycle FET did not improve the ongoing pregnancy rate.

WHAT IS KNOWN ALREADY

The use of luteal phase support in stimulated cycles has been associated with higher live-birth rates and the results are similar when using hCG or progesterone.

STUDY DESIGN SIZE, DURATION

This is a randomized double-blinded controlled trial of 450 women recruited between August 2013 and October 2015.

PARTICIPANTS/MATERIALS SETTING METHODS

Women with regular cycles undergoing natural cycle FET were recruited. Serial serum hormonal concentrations were used to time natural ovulation and at least Day 2 cleavage embryos were replaced. Patients were randomized into either: (i) the treatment group, receiving 1500 IU hCG on the day of FET and 6 days after FET, or (ii) the control group, receiving normal saline on these 2 days.

MAIN RESULTS AND THE ROLE OF CHANCE

The ongoing pregnancy rate [60/225 (26.7%) in the treatment group vs 70/225 (31.3%) in the control group, odds ratio 1.242 (95% CI 0.825-1.869)], implantation rate and miscarriage rate were comparable between the two groups. In the treatment group, there were significantly more cycles with top quality embryos transferred and a significantly higher serum oestradiol level, but a comparable serum progesterone level, 6 days after FET. However, no significant differences were observed in serum oestradiol and progesterone levels 6 days after FET between the pregnant and non-pregnant women. In the multivariate logistic regression, the number of embryos transferred was the only significant factor predictive of the ongoing pregnancy rate after natural cycle FET.

LIMITATIONS REASON FOR CAUTION

This study only included FET with cleavage stage embryos and only hCG, not vaginal progesterone, was used as luteal phase support.

WIDER IMPLANTATIONS OF THE FINDINGS

The findings in this study do not support the use of hCG for luteal phase support in natural cycle FET.

STUDY FUNDING/COMPETING INTERESTS

No external funding was used and there were no competing interests.

TRIAL REGISTRATION NUMBER

clinicaltrial.gov identifier: NCT01931384.

TRIAL REGISTRATION DATE

23/8/2013.

DATE OF FIRST PATIENT'S ENROLMENT

30/8/2013.

Endometrial development and function in experimentally induced luteal phase deficiency

CONTEXT

It is generally assumed that delayed endometrial development observed in luteal phase deficiency (LPD) is the result of abnormally low progesterone (P) levels. This hypothesis has never been tested by direct experiment.

OBJECTIVE

Our objective was to evaluate the effects of P concentrations on human endometrium.

DESIGN AND SETTING

A randomized trial was conducted at an academic medical center.

SUBJECTS

Twenty-nine healthy, ovulatory 18- to 35-yr-old women participated.

INTERVENTION

Endometrial samples were obtained from women in natural cycles and two groups of experimentally modeled cycles. Women undergoing modeled cycles were treated with GnRH agonist and a fixed physiological dose of transdermal estradiol, followed by randomization to 10 or 40 mg daily im P administration to achieve either normal circulating luteal P or 4-fold lower P concentrations, the latter representing an experimental model of LPD.

MAIN OUTCOME MEASURES

Tissue specimens, obtained after 10 days of P exposure, were analyzed by histological dating, immunohistochemistry, immunoblot, and real-time quantitative RT-PCR (qRT-PCR).

RESULTS

Histological dating of endometrium, immunohistochemistry for endometrial integrins, and qRT-PCR analysis for nine putative functional markers showed no differences between the three groups. Preliminary data from Western analysis suggest that some proteins may be affected by low serum P concentrations.

CONCLUSIONS

Histological endometrial dating does not reflect circulating P concentrations and cannot serve as a reliable bioassay of the quality of luteal function. Assessment of selected functional markers by either immunohistochemistry or qRT-PCR is similarly insensitive to decreased circulating P. Preliminary evidence suggests that abnormally low luteal phase serum P concentrations may have important functional consequences not otherwise detected.

Rescue of the corpus luteum in human pregnancy

Rescue of the corpus luteum from its programmed senescence maintains progesterone production required for pregnancy. In primates, chorionic gonadotropin produced by the developing conceptus acts as the primary luteotrophic signal. The purpose of this research was to assess corpus luteum rescue by examining changes in daily urinary progesterone metabolite levels during the first week after implantation. We determined the variability in progesterone metabolite profiles and evaluated its relationship to early pregnancy loss in 120 naturally conceived human pregnancies, including 43 early pregnancy losses. In other primates, an abrupt increase in the progesterone metabolite occurs at the time of implantation. This pattern occurred in an estimated 45% of the pregnancies in the present study. In the remaining pregnancies, there was a delayed rise (18%), neither a rise or decline (22%), or a decline (15%) during the week after implantation. The estimated rate of early pregnancy loss increased across these categories (from 5% loss with an abrupt rise at implantation to 100% loss with progesterone metabolite decline). Low urinary hCG levels in early pregnancy were significant determinants of a decline in postimplantation progesterone metabolite. However, preimplantation steroid metabolite levels were not significant, suggesting no inherent problem with the corpus luteum. Examination of individual progesterone metabolite profiles in relation to hCG profiles also indicated that few losses were caused by corpus luteum failure. Delineating the functional importance of an abrupt progesterone rise at the time of implantation may provide new strategies for promoting successful implantation in assisted reproduction.

Progesterone and ovulation

The role of progesterone (P) in the mechanism of ovulation is controversial at best. The contraceptive application of P was established in rodents in 1936 and with orally absorbed progestogenes was put to human use. There were hints on the proovulatory actions of P administered before the time of ovulation in rats by 1948. Similarly, in 1954 the observation of high P level in the preovulatory follicle pointed to a role in ovulation. Neither of these two observations was further investigated and the positive feedback effect of P exerted on gonadotropins was described in 1968. Still the positive feedback between P and gonadotropins were not recognized as a physiologic mechanism, much less utilized pharmacologically. The apparent contradiction between these two different actions of P continues upto now. The paper sets out to expose this controversy and tries to resolve it using extensive literary data and the author's experiences with synthetic progestogenes in contraception, in the treatment of infertility and with the antigestagen mifepristone in blocking ovulation. The precise mechanisms lying behind these applications are explored and discussed in detail. The putative role of oestradiol (E2) in the mechanism of eliciting the gonadotropin surge is extensively discussed but refuted as the ovulatory signal. The time sequence between the rise of P and gonadotropins contradicts the common wisdom of LH causing luteinization. The positive feedback effect of P on the E2 sensitized ovulatory axis on the hypothalamic and pituitary level is discussed and its local role in the mechanism of follicular rupture is also taken into account. The final proof seems to be the antiovulatory effect of mifepristone, which blocked both GnRH pulsatility, pituitary sensitivity to GnRH and follicular rupture in several experiments. Thus, the dogma of LH peak causing follicular rupture and subsequent luteinization seems questionable, the putative role of E2 to initiate the ovulatory cascade has to be discarded and P's role as a trigger of the physiological mechanisms leading to ovulation should be firmly recognized.

Expression of 3beta-hydroxysteroid dehydrogenase, cytochrome p450 17alpha-hydroxylase/17,20-lyase and cytochrome p450 aromatase enzymes in corpora lutea of diestrous and early pregnant mares

In the pregnant mare, luteal estrogen production increases at the onset of equine chorionic gonadotropin (eCG) secretion by endometrial cups. In previous studies, we have demonstrated that eCG stimulates luteal androgen and estrogen production in pregnant mares. To further elucidate the regulation of steroidogenesis within the equine corpus luteum (CL) of pregnancy, we examined the expression of 3beta-hydroxysteroid dehydrogenase (3beta-HSD), cytochrome P450 17alpha-hydroxylase/17,20 lyase (P450(17alpha)) and cytochrome P450 aromatase (P450(arom)) in luteal tissue samples collected during diestrus (Days 7 to 10) and pregnancy before (Days 29 to 35) and after (Days 42 to 45) the onset of eCG secretion. Immunoblot analyses revealed a single protein per enzyme with molecular weights of 48 kDa (3beta-HSD), 58 kDa (P450(17alpha)) and 56 kDa (P450(arom)). Steady-state levels of 3beta-HSD were lower in luteal tissue of diestrus than pregnancy, but expression did not change during pregnancy. Steady-state expression of P450(17alpha) in CL of diestrus was not significantly different from that of pregnancy. During pregnancy, P450(17alpha) expression was significantly higher after the onset of eCG secretion. Steady-state expression of P450(arom) in CL of diestrus was not significantly different from that of pregnancy. During pregnancy, luteal expression of P450(arom) was significantly lower after the onset of eCG secretion. These data support the hypotheses that eCG has a differential effect on the expression of luteal steroidogenic enzymes, that the eCG-induced increase in luteal estrogen production is the result of an increase in available aromatizable androgen due to an increase in P450(17alpha) expression and activity, and that increased luteal estrogen production is not due to an increase in aromatase expression.

Corpus luteum response to exogenous HCG during the mid-luteal phase of the menstrual cycle

OBJECTIVE

To assess a range of exogenous HCG regimes designed to simulate the endocrine environment occurring in biochemical, single and multiple pregnancies and to study the response of the corpus luteum to those regimes.

DESIGN

Prospective clinical study.

PATIENTS

Twenty-five normally cycling women aged 24-35 years were given one of four regimes of HCG injections designed to mimic the HCG concentrations found following spontaneous implantation. Regimes A, B, C and D were designed with starting HCG doses of 60, 140, 250 and 1000 iu, respectively. The daily HCG injections were then increased to give a doubling concentration every 30 h for regime A, every 27 h for regime B, every 24 h for regimes C and D. HCG administration was started on either days 7 or 8 after the LH peak.

MEASUREMENTS

Plasma HCG and progesterone concentrations.

RESULTS

Subjects given regime A failed to demonstrate any rescue of the corpus luteum despite low-detectable amounts of HCG in the circulation equivalent to those seen in some biochemical pregnancies. In contrast, subjects given regimes B and C demonstrated prompt increases in progesterone secretion immediately after the first HCG injection achieving HCG and progesterone concentrations in plasma similar to those seen in normal singleton pregnancies. Subjects given regime D also showed rapid rescue of the corpus luteum but this time achieved plasma HCG concentrations in the range normally seen in multiple pregnancies. All subjects in regimes B, C and D secreted significantly higher amounts of progesterone than those in regime A (P<0.001). However, despite the greater amounts of HCG used in regime D, the amount of progesterone produced was not significantly different from regimes B or C.

CONCLUSIONS

The exogenous HCG regimes used in this study successfully mimicked the hormonal environment found in biochemical, single and multiple pregnancies and elicited appropriate corpus luteum responses.

The optimum time for exogenous human chorionic gonadotropin to rescue the corpus luteum

PURPOSE

Our purpose was to study the optimum time to administer exogenous human chorionic gonadotropin (hCG) to rescue the human corpus luteum during the luteal phase of normal menstrual cycles.

METHODS

Groups of normally cycling women were given 4-day regimes of exogenous hCG by daily injection beginning 4 (Group A), 8 (Group B), and 12 (Group C) days after the midcycle luteinizing hormone surge. The hCG regime used was designed to mimic hCG levels following a spontaneous implantation. All subjects acted as their own controls in a preceding normal menstrual cycle.

RESULTS

Group A subjects exhibited patterns and levels of salivary progesterone concentration similar to those seen in the control cycles throughout the normal luteal phase. In contrast, subjects in both Group B and Group C demonstrated a rapid and sustained increase in progesterone production following the hCG injections. Furthermore, subjects in Group B achieved the highest mean peak progesterone concentrations and the total amount of salivary progesterone secreted was significantly higher than in the control cycles (P < 0.05). Although the mean luteal-phase length was greatest in Group C, the response of the corpus luteum was suboptimal, with a delayed rise in salivary progesterone.

CONCLUSIONS

These data show that the qualitative and quantitative response of corpus luteum to an early pregnancy-type hCG signal is maximal around the midluteal phase, coincident with the time of implantation.

Luteal phase consequences of low-dose gonadotropin-releasing hormone agonist therapy in nonluteal-supported in vitro fertilization cycles

OBJECTIVE

To determine the follicular and luteal phase impact of low-dose GnRH agonist (GnRH-a) treatment during follicular stimulation for IVF.

DESIGN

A randomized prospective study compared patients receiving low-dose GnRH-a and hMG therapy to clomiphene citrate (CC) and hMG cycles.

SETTING

Patients were treated through a university-based IVF-ET program.

PATIENTS

Thirty-six patients underwent follicular stimulation with low-dose GnRH-a and hMG and were compared with 34 patients undergoing ovulation induction with CC and hMG.

RESULTS

Significantly shorter luteal phase length occurred with GnRH-a and hMG therapy; however, there was no statistically significant difference in luteal P levels. Follicular parameters were the same (peak E2, number of follicles, and number of oocytes), suggesting that folliculogenesis was not altered. There were no statistical differences in pregnancy rates.

CONCLUSIONS

Sustained low-dose GnRH-a therapy during follicular stimulation does not have a clinical effect on luteal function.

Regulation of early gestational corpus luteum function in spontaneous and follicular stimulated conceptions

OBJECTIVE

To determine the regulatory role of hCG on P secretion in normal and abnormal (abortive and ectopic) first trimester pregnancies.

STUDY DESIGN

The number of doublings of hCG per day (1/DT; reciprocal of hCG doubling time) was correlated with serum P using linear and nonlinear models in normal intrauterine pregnancies, spontaneous abortions, and ectopic pregnancies (EPs) conceived spontaneously or after clomiphene citrate (CC).

RESULTS

Linear correlations between P and 1/DTs of hCG were poor. In contrast, nonlinear modeling with a hyperbolic curve fit the data well and allowed all of the data to be included for analysis regardless of the pregnancy type. Furthermore, this model could be used to explain the differential P concentrations seen in normal and abnormal first trimester pregnancies. The nonlinear hyperbolic model demonstrated that follicular events determine the maximal P production during early gestation. Human chorionic gonadotropin 1/DTs approximately equal to 0.5 sustain maximal P production. Progesterone production is then sustained by the rate of change of hCG.

CONCLUSION

Nonlinear correlation analysis suggests that P production in early gestations is regulated by prior follicular events and the rate of hCG production.

Comparison of leuprolide acetate and human chorionic gonadotropin for the induction of ovulation in clomiphene citrate-stimulated cycles

OBJECTIVE

To examine the relative efficacies of leuprolide acetate (LA) and hCG in inducing ovulation and a normal luteal phase during clomiphene citrate (CC)-stimulated superovulation cycles.

DESIGN

Prospective, randomized, blinded, and cross-controlled in consecutive cycles.

SETTING

Large military tertiary care center.

PATIENTS

Twenty-one ovulatory patients undergoing superovulation with CC and IUIs for the treatment of unexplained or male factor infertility.

INTERVENTIONS

Clomiphene citrate (100 mg/d) on cycle days 5 through 9 in both of the study cycles. Administration of 2 mg SC LA in one cycle and 10,000 IU IM hCG in another cycle for induction of the midcycle surge.

MAIN OUTCOME MEASURES

Serum LH, FSH, E2, and P levels every 12 hours for 36 hours after administration of either LA or hCG to characterize the midcycle hormonal dynamics. Luteal phase duration and serum P levels during the midluteal phase were used to estimate the adequacy of the luteal phase. Serial ultrasounds also were done to determine the incidence of luteinized unruptured follicle syndrome.

RESULTS

Serum FSH levels in the periovulatory interval were significantly higher after the administration of LA. There were no differences in the periovulatory E2 or P levels or the incidence of sonographic evidence of ovulation after administration of either LA or hCG. Although midluteal serum P levels were higher in the cycles in which hCG was administered, all 42 treatment cycles had adequate luteal phases as assessed by luteal phase duration and three midluteal P levels. Ongoing pregnancies occurred after both LA- and hCG-stimulated cycles.

CONCLUSION

Leuprolide acetate and hCG were equivalent in their abilities to induce ovulation. Further evaluation of the adequacy of the luteal phase and the ensuing pregnancy rates after LA induction of an endogenous gonadotropin surge are indicated.

The significance of plasma progesterone levels during early pregnancies achieved after in vitro fertilization (IVF) treatment

OBJECTIVE

Corpus luteum steroidogenesis is lower for in vivo ectopic pregnancy than for intrauterine pregnancy. There is a progesterone hallmark level distinguishing between viable intrauterine pregnancy and nonviable or ectopic pregnancy. This study attempts to answer whether this is also true for in vitro fertilization-treated patients.

STUDY DESIGN

Using information retrieved from a computerized database, we compared the plasma 17 beta-estradiol (E2) and progesterone during the luteal phase and for every 2 to 3 days for several weeks during early pregnancy between those patients with proven ectopic pregnancies and those with singleton and multiple intrauterine pregnancies. Vaginal ultrasonography to detect an intrauterine gestational sac was performed from day 19. A total of 73 pregnancies resulted from the replacement of fresh embryos in our in vitro fertilization-embryo transfer program.

RESULTS

Only at day 10 post embryo transfer did those patients with ectopic pregnancy show statistically lower mean (SD) serum levels of E2 [2257 (SD, 2351) pmol/L] and plasma progesterone [PP; 221 (SD, 283) nmol/L] compared with patients with intrauterine pregnancy, whose mean E2 was 8846 (SD, 5871) pmol/L and mean PP was 805 (SD, 582) nmol/L (P = 0.008). For the rest of the follow-up until surgery was performed in ectopic pregnancy, there were no differences of statistical significance between extrauterine pregnancy and the intrauterine pregnancy groups. Furthermore, only on day 10 post embryo transfer, did we find a discriminatory zone (confidence interval, 95%) for E2 levels (903 to 3502 pmol/L for EP vs 6116 to 9493 pmol/L for a singleton and 4875 to 9493 pmol/L for multiple pregnancies). PP levels were 26 to 283 nmol/L for ectopic pregnancy versus 496 to 1096 nmol/L for both singleton and multiple pregnancies. An intrauterine gestational sac was visualized at a mean of 23.2 (SD, 4) days after embryo transfer. On this day, the mean P levels were 982.6 (SD, 286.2) nmol/L for intrauterine and 804.5 (SD, 502.4) nmol/L for ectopic pregnancies (P = NS).

CONCLUSIONS

Except for day 10 post embryo transfer, the steroidogenesis in ectopic pregnancy after in vitro fertilization treatment does not differ from successful intrauterine pregnancy. This observation negates an impaired steroidogenesis for ectopic pregnancy after in vitro fertilization and makes the PP level irrelevant in the diagnosis of pregnancy implantation.