Letrozole vs. clomiphene citrate in patients with ovulatory infertility

The definition of unexplained infertility: A systematic review

BACKGROUND

There is no consensus on tests required to either diagnose unexplained infertility or use for research inclusion criteria. This leads to heterogeneity and bias affecting meta-analysis and best practice advice.

OBJECTIVES

This systematic review analyses the variability of inclusion criteria applied to couples with unexplained infertility. We propose standardised criteria for use both in future research studies and clinical diagnosis.

SEARCH STRATEGY

CINAHL and MEDLINE online databases were searched up to November 2022 for all published studies recruiting couples with unexplained infertility, available in full text in the English language.

DATA COLLECTION AND ANALYSIS

Data were collected in an Excel spreadsheet. Results were analysed per category and methodology or reference range.

MAIN RESULTS

Of 375 relevant studies, only 258 defined their inclusion criteria. The most commonly applied inclusion criteria were semen analysis, tubal patency and assessment of ovulation in 220 (85%), 232 (90%), 205 (79.5%) respectively. Only 87/220 (39.5%) studies reporting semen analysis used the World Health Organization (WHO) limits. Tubal patency was accepted if bilateral in 145/232 (62.5%) and if unilateral in 24/232 (10.3%). Ovulation was assessed using mid-luteal serum progesterone in 115/205 (56.1%) and by a history of regular cycles in 87/205 (42.4%). Other criteria, including uterine cavity assessment and hormone profile, were applied in less than 50% of included studies.

CONCLUSIONS

This review highlights the heterogeneity among studied populations with unexplained infertility. Development and application of internationally accepted criteria will improve the quality of research and future clinical care.

A Review on the Use of Letrozole in Female and Male Infertility

Infertility in developing countries is a distinct and complex problem that disproportionately affects women. Though not a physically restraining disease, it causes a huge social burden on the emotional, financial, and psychosocial quotients of those who suffer from it. Assisted reproductive procedures are frequently used to treat infertility. Years ago, the emergence of ovulation induction represented a significant advancement in treating female infertility. Letrozole, an aromatase inhibitor, is a potential therapy for ovulation induction. Numerous clinical conditions, including anovulatory infertility, polycystic ovarian syndrome, unexplained infertility, and early stages of endometriosis-related infertility, as well as many with improved live birth rates, have been proven to benefit from letrozole treatment. Letrozole is a superior alternative to the widely utilized ovulation induction with clomiphene citrate. While clomiphene citrate has certain limitations, letrozole successfully overcomes these limitations because of its lack of prolonged anti-estrogenic activity, short half-life, and lack of estrogen receptor activation. In most cases, this results in mono-follicular development and excellent live birth rates. According to the most recent research, letrozole can be used as the first-line therapy to treat infertility caused by polycystic ovarian syndrome and other causes. Letrozole is also emerging as a possible treatment for male infertility of unknown cause, proving to be an effective way of influencing hormonal profiles and increasing various seminal parameters such as sperm motility and concentration, as it inhibits aromatization affecting the feedback mechanism to the hypothalamus. This review focuses on our current knowledge of the uses of letrozole for female and male infertility, its mechanisms, and its benefits.

D-chiro-inositol Induces Ovulation in Non-Polycystic Ovary Syndrome (PCOS), Non-Insulin-Resistant Young Women, Likely by Modulating Aromatase Expression: A Report of 2 Cases

Case series

Patients: Female, 19-year-old • Female, 23-year-old

Final Diagnosis: Anovulation

Symptoms: Oligomenorrhea

Medication: —

Clinical Procedure: —

Specialty: Obstetrics and Gynecology

Letrozole for Female Infertility

Letrozole, an aromatase inhibitor that blocks estrogen synthesis by inhibiting the final step of the estrogen biosynthetic pathway, has been used in the applications of a wide range of infertility settings. It has been more than 20 years since the initial clinical trial of letrozole for ovulation induction. In light of the accumulating clinical and basic evidence, the efficacy and safety of letrozole have been identified. This mini review focuses on our current knowledge of the applications and mechanisms of letrozole for female infertility and various questions are put forward about how letrozole could be more effectively used.

Risk of foetal harm with letrozole use in fertility treatment: a systematic review and meta-analysis

BACKGROUND

The aromatase inhibitor letrozole is increasingly recommended for ovulation induction, as it is more effective with fewer side-effects than other agents. But many clinicians are reluctant to use the drug for fertility treatment due to a strong-label warning against its use, which warns about congenital malformation risk to the foetus in women seeking pregnancy.

OBJECTIVE AND RATIONALE

The aim of this study was to determine the risks of congenital malformations and pregnancy loss with letrozole compared with clomiphene primarily, and with other fertility drugs and natural conception.

SEARCH METHODS

A systematic review and meta-analysis using PRISMA harms guidelines. We searched MEDLINE, EMBASE and other sources from inception until January 2020, with the MeSH words for 'letrozole' and pregnancy OR foetal/neonatal outcome. We included studies reported on congenital malformations in foetuses born to mothers conceived after fertility treatment, with letrozole versus clomiphene, placebo, gonadotrophins, metformin, natural conception or other agents, from randomised trials, comparative cohort studies and non-comparative observational cohorts. Quality of the studies was assessed using Cochrane risk of bias tool and Newcastle Ottawa Scale. The McMaster tool was used to assess the quality of reported harm for foetal congenital malformations in the studies. We compared the absolute risk of events using risk difference measures and pooled the findings using a fixed-effect model. We evaluated the statistical heterogeneity using forest plots and the I2 statistic and funnel plot to assess publication bias. We assessed the strength of evidence for congenital malformation and pregnancy loss as per the GRADE recommendations and with the Fragility index.

OUTCOMES

We included 46 studies (18 randomised trials; 21 comparative cohorts; 7 non-comparative cohorts). Overall 2.15% (101/4697; 95% CI 1.7 to 2.5) of babies conceived on letrozole for fertility treatment had congenital foetal malformations. We did not observe a significant increase in congenital malformations with letrozole versus clomiphene in the randomised trials (risk difference (RD) 0.01, 95% CI -0.02, 0.03; I2 = 0%; 14 studies) and found a significant reduction in the cohort studies (RD -0.02, 95% CI -0.04, -0.01; I2 = 0%, 11 studies). The fragility index was 44% (7/16) (either an increase in the intervention arm or a decrease in control arm was needed to alter the results). The risks of pregnancy loss were not increased with letrozole versus clomiphene in the 14 randomised trials (RD -0.01, 95% CI -0.06, 0.04; I2 = 0%), and the risks were reduced in the six cohort studies (RD -0.09, 95% CI -0.17, -0.00; I2 = 68%). The GRADE quality of evidence was low to moderate for congenital malformations and pregnancy loss. We did not find any increased congenital malformation risk with letrozole versus gonadotrophins, natural conception or natural cycle ART, but the number of studies was small.

WIDER IMPLICATIONS

There is no evidence that letrozole increases the risk of congenital foetal malformation or pregnancy loss compared with clomiphene, natural conception or other fertility agents, to warrant warning against its use. Given its therapeutic benefits and lack of evidence of harm to the foetus, clinicians should consider letrozole as first-line agent for ovulation induction.

Predictive factors for intrauterine insemination outcomes: a review

PURPOSE

Intrauterine insemination (IUI) is a frequently utilized method of assisted reproduction for patients with mild male factor infertility, anovulation, endometriosis, and unexplained infertility. The purpose of this review is to discuss factors that affect IUI outcomes, including infertility diagnosis, semen parameters, and stimulation regimens.

METHODS

We reviewed the published literature to evaluate how patient and cycle specific factors affect IUI outcomes, specifically clinical pregnancy rate, live birth rate, spontaneous abortion rate and multiple pregnancy rate.

RESULTS

Most data support IUI for men with a total motile count > 5 million and post-wash sperm count > 1 million. High sperm DNA fragmentation does not consistently affect pregnancy rates in IUI cycles. Advancing maternal and paternal age negatively impact pregnancy rates. Paternal obesity contributes to infertility while elevated maternal BMI increases medication requirements without impacting pregnancy outcomes. For ovulation induction, letrozole and clomiphene citrate result in similar pregnancy outcomes and are recommended over gonadotropins given increased risk for multiple pregnancies with gonadotropins. Letrozole is preferred for obese women with polycystic ovary syndrome. IUI is most effective for women with ovulatory dysfunction and unexplained infertility, and least effective for women with tubal factor and stage III-IV endometriosis. Outcomes are similar when IUI is performed with ovulation trigger or spontaneous ovulatory surge, and ovulation may be monitored by urine or serum. Most pregnancies occur within the first four IUI cycles, after which in vitro fertilization should be considered.

CONCLUSIONS

Providers recommending IUI for treatment of infertility should take into account all of these factors when evaluating patients and making treatment recommendations.

Effect of orally administrated letrozole on reproduction performance and gene expression of FOXJ1, LPR2 and PVRL3 in reproductive tract in aged roosters

letrozole is an aromatase inhibitor that stops the production of estrogen through interrupting the entrance of hormone androgen into a small amount of estrogen. Therefore, the current study was developed to estimate orally administrated Letrozole on the reproductive performance and relative abundance of Foxj1, PVRL3, and LPR2 mRNA in aged roosters. Fifty-five-week old ROSS 308 breeder roosters (n = 18) were orally treated using letrozole. Primarily, the body weight of the animals was recorded, and they were randomly classified into three groups (n = 6 birds/group) receiving different doses of Letrozole, including 0, 0.015, and 0.03 mg/kg body weight/day for three weeks. At the end of the trial, seminal traits, plasma, testicular hormone levels (testosterone, estradiol, and FSH), histopathological studies, in vitro fertility, and relative abundance of testis PVRL3, epidydimal Foxj1, and LPR2 mRNA were evaluated. Based on the results, the sperm quality variables were statistically higher in the 0.03 group compared to the controls. Greater histologic parameters, such as diameter of seminiferous tubules, thickness of seminiferous epithelium, categorized epididymal region, and in vitro fertility rates were estimated for the treated groups(p < 0.001). Plasma and testicular testosterone, estradiol concentrations, and plasma FSH levels were significantly influenced by letrozll treatment (p < 0.001). Relative mRNA transcript abundance increased for PVRL3 and decreased for Foxj1 and LPR2 in treated groups. Overall, aromatase inhibitors can enhance the reproductive performance of aged commercial broiler breeder roosters. However, it can impact endocytosis and ciliogenesis events via reducing estradiol.

IUI for unexplained infertility-a network meta-analysis

BACKGROUND

IUI for unexplained infertility can be performed in a natural cycle or in combination with ovarian stimulation. A disadvantage of ovarian stimulation is an increased risk of multiple pregnancies with its inherent maternal and neonatal complication risks. Stimulation agents for ovarian stimulation are clomiphene citrate (CC), Letrozole or gonadotrophins. Although studies have compared two or three of these drugs to each other in IUI, they have never been compared to one another in one analysis.

OBJECTIVE AND RATIONALE

The objective of this network meta-analysis was to compare the effectiveness and safety of IUI with CC, Letrozole or gonadotrophins with each other and with natural cycle IUI.

SEARCH METHODS

We searched PubMed, MEDLINE, EMBASE, Cochrane Database of Systematic Reviews, CENTRAL and the Clinical Trial Registration Database indexed up to 16 August 2018. We included randomized controlled trials that compared a stimulation regimen with CC, Letrozole or gonadotrophins to each other or to natural cycle IUI among couples with unexplained infertility. We performed the network meta-analysis within a multivariate random effects model.

OUTCOMES

We identified 26 studies reporting on 5316 women. The relative risk (RR) for live birth/ongoing pregnancy rates comparing IUI with CC to natural cycle IUI was 1.05 (95% CI 0.63-1.77, low quality of evidence), while comparing IUI with Letrozole to natural cycle IUI was 1.15 (95% CI 0.63-2.08, low quality of evidence) and comparing IUI with gonadotrophins to natural cycle IUI was 1.46 (95% CI 0.92-2.30, low quality of evidence). The RR for live birth/ongoing pregnancy rates comparing gonadotrophins to CC was 1.39 (95% CI 1.09-1.76, moderate quality of evidence), comparing Letrozole to CC was 1.09 (95% CI 0.76-1.57, moderate quality of evidence) and comparing Letrozole to gonadotrophins was 0.79 (95% CI 0.54-1.15, moderate quality of evidence). We did not perform network meta-analysis on multiple pregnancy due to high inconsistency. Pairwise meta-analyses showed an RR for multiple pregnancy rates of 9.11(95% CI 1.18-70.32) comparing IUI with gonadotrophins to natural cycle IUI. There was no data available on multiple pregnancy rates following IUI with CC or Letrozole compared to natural cycle IUI. The RR for multiple pregnancy rates comparing gonadotrophins to CC was 1.42 (95% CI 0.68-2.97), comparing Letrozole to CC was 0.97 (95% CI 0.47-2.01) and comparing Letrozole to gonadotrophins was 0.29 (95% CI 0.14-0.58).In a meta-analysis among studies with adherence to strict cancellation criteria, the RR for live births/ongoing pregnancy rates comparing gonadotrophins to CC was 1.20 (95% CI 0.95-1.51) and the RR for multiple pregnancy rates comparing gonadotropins to CC was 0.80 (95% CI 0.38-1.68).

WIDER IMPLICATIONS

Based on low to moderate quality of evidence in this network meta-analysis, IUI with gonadotrophins ranked highest on live birth/ongoing pregnancy rates, but women undergoing this treatment protocol were also at risk for multiple pregnancies with high complication rates. IUI regimens with adherence to strict cancellation criteria led to an acceptable multiple pregnancy rate without compromising the effectiveness. Within a protocol with adherence to strict cancellation criteria, gonadotrophins seem to improve live birth/ongoing pregnancy rates compared to CC. We, therefore, suggest performing IUI with ovarian stimulation using gonadotrophins within a protocol that includes strict cancellation criteria. Obviously, this ignores the impact of costs and patients preference.

Evidence-based treatments for couples with unexplained infertility: a guideline

OBJECTIVE

To provide evidence-based recommendations to practicing physicians and others regarding the effectiveness and safety of therapies for unexplained infertility.

METHODS

ASRM conducted a literature search, which included systematic reviews, meta-analyses, randomized controlled trials, and prospective and retrospective comparative observational studies published from 1968 through 2019. The ASRM Practice Committee and a task force of experts used available evidence and informal consensus to develop evidence-based guideline recommendations.

MAIN OUTCOME MEASURE(S)

Outcomes of interest included: live-birth rate, clinical pregnancy rate, implantation rate, fertilization rate, multiple pregnancy rate, dose of treatment, rate of ovarian hyperstimulation, abortion rate, and ectopic pregnancy rate.

RESULT(S)

The literature search identified 88 relevant studies to inform the evidence base for this guideline.

RECOMMENDATION(S)

Evidence-based recommendations were developed for the following treatments for couples with unexplained infertility: natural cycle with intrauterine insemination (IUI); clomiphene citrate with intercourse; aromatase inhibitors with intercourse; gonadotropins with intercourse; clomiphene citrate with IUI; aromatase inhibitors with IUI; combination of clomiphene citrate or letrozole and gonadotropins (low dose and conventional dose) with IUI; low-dose gonadotropins with IUI; conventional-dose gonadotropins with IUI; timing of IUI; and in vitro fertilization and treatment paradigms.

CONCLUSION(S)

The treatment of unexplained infertility is by necessity empiric. For most couples, the best initial therapy is a course (typically 3 or 4 cycles) of ovarian stimulation with oral medications and intrauterine insemination (OS-IUI) followed by in vitro fertilization for those unsuccessful with OS-IUI treatments.

A Study of Controlled Ovarian Stimulation with Clomiphene Citrate or Letrozole in Combination with Gonadotropins and IUI in Unexplained Infertility

Aim:

To compare the effect of clomiphene citrate (CC) + human menopausal gonadotropin (hMG) with letrozole + hMG on size, number of follicles, endometrial thickness, serum levels of oestradiol and progesterone and pregnancy rate.

Settings and Design:

Non-randomised interventional study.

Patients and Methods:

A total number of 60 patients in the age group of 20–35 years with unexplained infertility were divided into two groups, 30 in each. Group A received CC + hMG and group B received letrozole + hMG. In both the groups, ovulation was triggered by hCG followed by intrauterine insemination.

Results:

The number of follicles on day 8 were significantly higher in the CC + hMG group than that in the letrozole + hMG group. Serum oestradiol level was significantly higher in the CC + hMG group on day 10 and on the day of hCG administration. Pregnancy rate in the CC + hMG group was 23.3% and 13.3% in the letrozole + hMG group.

Conclusion:

The sequential protocol was cost-effective. CC + hMG could be a preferred ovarian stimulation protocol in couples with unexplained infertility with the added advantage of having no significant complications in properly monitored cycles.

Oral Drugs for Unexplained Infertility

Of the infertile couples unable to conceive without any identifiable cause, 30 % are defined as having unexplained infertility. Management depends on duration of infertility and age of female partner. The treatment of unexplained infertility is empirical, and many different regimens have been used. Among these are expectant management, ovarian stimulation with clomiphene citrate, gonadotropins and aromatase inhibitors, fallopian tube sperm perfusion, tubal flushing, intrauterine insemination, gamete intrafallopian transfer, and IVF. The first approach to treatment of unexplained infertility generally is the use of drugs that stimulate oocyte production. For over four decades, the first-line treatment for ovarian stimulation in unexplained infertility has been clomiphene citrate. Multiple reports suggest that aromatase inhibitors may be effective alternative agents for ovarian stimulation in couples with unexplained infertility. Their administration is reported to be associated with monofollicular development in most cases, which may result in enhanced fertility and a reduced risk of ovarian hyperstimulation and multiple births, as compared to current standard therapies such as gonadotropin and clomiphene. Despite world evidence to the contrary, letrozole has been banned for use for infertility management in India since 2011.

Letrozole, Gonadotropin, or Clomiphene for Unexplained Infertility

BACKGROUND

The standard therapy for women with unexplained infertility is gonadotropin or clomiphene citrate. Ovarian stimulation with letrozole has been proposed to reduce multiple gestations while maintaining live birth rates.

METHODS

We enrolled couples with unexplained infertility in a multicenter, randomized trial. Ovulatory women 18 to 40 years of age with at least one patent fallopian tube were randomly assigned to ovarian stimulation (up to four cycles) with gonadotropin (301 women), clomiphene (300), or letrozole (299). The primary outcome was the rate of multiple gestations among women with clinical pregnancies.

RESULTS

After treatment with gonadotropin, clomiphene, or letrozole, clinical pregnancies occurred in 35.5%, 28.3%, and 22.4% of cycles, and live birth in 32.2%, 23.3%, and 18.7%, respectively; pregnancy rates with letrozole were significantly lower than the rates with standard therapy (gonadotropin or clomiphene) (P=0.003) or gonadotropin alone (P<0.001) but not with clomiphene alone (P=0.10). Among ongoing pregnancies with fetal heart activity, the multiple gestation rate with letrozole (9 of 67 pregnancies, 13%) did not differ significantly from the rate with gonadotropin or clomiphene (42 of 192, 22%; P=0.15) or clomiphene alone (8 of 85, 9%; P=0.44) but was lower than the rate with gonadotropin alone (34 of 107, 32%; P=0.006). All multiple gestations in the clomiphene and letrozole groups were twins, whereas gonadotropin treatment resulted in 24 twin and 10 triplet gestations. There were no significant differences among groups in the frequencies of congenital anomalies or major fetal and neonatal complications.

CONCLUSIONS

In women with unexplained infertility, ovarian stimulation with letrozole resulted in a significantly lower frequency of multiple gestation but also a lower frequency of live birth, as compared with gonadotropin but not as compared with clomiphene. (Funded by the National Institutes of Health and others; ClinicalTrials.gov number, NCT01044862.).

Are uterine and ovarian artery Doppler velocimetry values good pregnancy predictors in clomiphene citrate cycles?

Background

We conducted this prospective study to evaluate the prognostic significance of uterine and ovarian artery Doppler velocimetry in clomiphene citrate (CC) cycles.

Materials and Methods

A total of 80 patients with unexplained infertility were given 100 mg/day of CC from day 3 to day 7 of their cycles in this current prospective study. On cycle day 3, before administration of CC, each patient underwent Doppler transvaginal ultrasonography. The Doppler velocimetries of the right and left uterine and ovarian arteries were recorded and analyzed in association with demographic and clinical parameters.

Results

TheThere were 6 out of 80 patients who became pregnant, the overall pregnancy rate in this population was 7.5% for the current study. The cases were divided into two groups according to whether they became pregnant or not. Demographic characteristics showed no statistically significant differences between these groups (p>0.05). However, the duration of infertility did show statistically significant differences between the groups. Doppler velocimetry was not statistically significantly different between the two groups.

Conclusion

Doppler velocimetry of the uterine and ovarian arteries is not a factor in the prognosis for pregnancy in CC cycles.

Assessment of multiple intrauterine gestations from ovarian stimulation (AMIGOS) trial: baseline characteristics

OBJECTIVE

To identify baseline characteristics of women with unexplained infertility to determine whether treatment with an aromatase inhibitor will result in a lower rate of multiple gestations than current standard ovulation induction medications.

DESIGN

Randomized, prospective clinical trial.

SETTING

Multicenter university-based clinical practices.

PATIENT(S)

A total of 900 couples with unexplained infertility.

INTERVENTION(S)

Collection of baseline demographics, blood samples, and ultrasonographic assessments.

MAIN OUTCOME MEASURE(S)

Demographic, laboratory, imaging, and survey characteristics.

RESULT(S)

Demographic characteristics of women receiving clomiphene citrate (CC), letrozole, or gonadotropins for ovarian stimulation were very consistent. Their mean age was 32.2 ± 4.4 years and infertility duration was 34.7 ± 25.7 months, with 59% primary infertility. More than one-third of the women were current or past smokers. The mean body mass index (BMI) was 27 and mean antimüllerian hormone level was 2.6; only 11 women (1.3%) had antral follicle counts of <5. Similar observations were identified for hormonal profiles, ultrasound characterization of the ovaries, semen parameters, and quality of life assessments in both male and female partners.

CONCLUSION(S)

The cause of infertility in the couples recruited to this treatment trial is elusive, as the women were regularly ovulating and had evidence of good ovarian reserve both by basal FSH, antimüllerian hormone levels, and antral follicle counts; the male partners had normal semen parameters. The three treatment groups have common baseline characteristics, thereby providing comparable patient populations for testing the hypothesis that use of letrozole for ovarian stimulation can reduce the rates of multiples from that observed with gonadotropin and CC treatment.

CLINICAL TRIAL REGISTRATION NUMBER

NCT 01044862.

Clinical use of fertility agents and risk of breast cancer: a recent update for an old problem

PURPOSE OF REVIEW

Female infertility is today a very common, expanding problem and therefore restoring fertility strategies are increasing in the last few years. An association between ovarian stimulation and breast cancer risk has been hypothesized, but the question has not yet been clarified.

RECENT FINDINGS

In the last 2 years, many important studies have been published on this topic. A lot of new combinations of drugs are in experimentation and other recent drugs are already in current use, such as aromatase inhibitors. Furthermore, the data from older studies were investigated by two recent meta-analyses.

SUMMARY

Infertility affects many couples in western countries and the use of fertility stimulation techniques is widespread in the last few years, determining personal anxiety, social costs, and organizing difficulties. It is well known that one of the most important causative agents for the development of breast cancer is the proliferative activity of endogenous and exogenous female hormones. Therefore, it seems appropriate to investigate the risk of breast cancer derived from the use of hormonal therapies in infertile women. The final clarification of this question is very important so that all women can realize their dream of having children, with the certainty of not being exposed to an increased risk of breast cancer.

A comparison of the efficacy of two doses of letrozole alone or with continuous recombinant follicle-stimulating hormone for ovulation induction in anovulatory women

AIMS

To determine the efficacy of letrozole alone or with recombinant follicle-stimulating hormone (rFSH) for ovarian induction in anovulatory women.

METHODS

A total of 322 patients undergoing intrauterine insemination (IUI) were included in this retrospective study. Letrozole (2.5 or 5.0 mg) was administered from days 5 to 9 of menses, alone or followed with rFSH started on day 9 until the day of human chorionic gonadotropin administration. A single IUI was performed 24 h after ovulation.

RESULTS

The number of follicles, endometrial thickness and serum estradiol levels were significantly higher in the letrozole + rFSH groups than in the letrozole-alone groups (p < 0.05), but no significant difference was found between the two doses of letrozole, whether alone or with rFSH. Women treated with 5.0 mg/day of letrozole + rFSH required a total dose of rFSH similar to women treated with 2.5 mg/day of letrozole + rFSH (230.77 ± 118.29 vs. 258.55 ± 130.13 IU, respectively; p = 0.205). There was no significant difference in pregnancy rates between the two doses of letrozole, whether alone or with rFSH.

CONCLUSION

Treatment with letrozole + rFSH was more efficacious than letrozole alone for pregnancy in the IUI program; however, the effect of 5.0 mg/day of letrozole versus 2.5 mg/day of letrozole on ovulation was equivalent, regardless of whether rFSH was used.

Molecular orbital studies (hardness, chemical potential and electrophilicity), vibrational investigation and theoretical NBO analysis of 4-4'-(1H-1,2,4-triazol-1-yl methylene) dibenzonitrile based on abinitio and DFT methods

The Fourier transform infrared (FTIR) and FT Raman (FTR) of 4-4'-(1H-1, 2, 4-triazol-1-yl methylene) dibenzonitrile (4-HTMDBN) have been recorded and analyzed. The equilibrium geometry harmonic vibrational frequencies have been investigated with the help of standard HF and DFT methods with 6-31G(d,p) as basis set. The assignments of the vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMFF). Theoretical simulations of the FTIR and FTR spectra of the title compound have been calculated. The (1)H and (13)C Nuclear Magnetic Resonance (NMR) chemical shifts of the molecule were calculated by the Gauge including atomic orbital (GIAO) method. The stability of the molecule has been analyzed using natural bond orbital (NBO) analysis. The linear polarizability (α) and the first order hyperpolarizability (β) values of the investigated molecule have been computed using HF/DFT/6-31G(d,p) methods on the finite field approach. UV-Vis spectrum of the compound is recorded and the electronic properties such as HOMO and LUMO energies, are performed. The directly calculated ionization potential (IP), electron affinity (EA), electronegativity (χ), electrophilicity index (ω), hardness (η) and chemical potential (ρ) are all correlated with the HOMO and LUMO energies with their molecular properties. Mulliken population analysis on atomic charges, molecular electrostatic potential maps (MEP) and thermodynamical properties of title compound at different temperature have been calculated.

Use of clomiphene citrate in infertile women: a committee opinion

This committee opinion describes the use of clomiphene citrate, including indications, use, monitoring, and side effects. There is also a discussion of adjuvants and alternatives to clomiphene citrate therapy.

Clinical review: The use of aromatase inhibitors for ovulation induction and superovulation

CONTEXT

Anovulation is likely responsible for 20% of female infertility. Although clomiphene citrate remains the first-line therapy for ovulation induction in anovulatory patients who are not estrogen-deficient and to treat unexplained infertility, there remains a discrepancy between ovulation and conception rates with its use, attributed to its antiestrogenic effects on cervical mucus and the endometrium. Alternative agents, including aromatase inhibitors, have been used that have not been associated with these side effects.

EVIDENCE ACQUISITION

A literature search was conducted to specifically explore the use of aromatase inhibitors for ovulation induction and superovulation.

EVIDENCE SYNTHESIS

Recent studies have found that aromatase inhibitors may be safe and useful agents for ovulation induction in patients with polycystic ovarian syndrome as well a treatment option for superovulation in patients with either unexplained infertility or endometriosis.

CONCLUSIONS

Aromatase inhibitors may be an effective alternative treatment to clomiphene citrate for both ovulation induction and superovulation.

Is letrozole superior to clomiphene for ovarian stimulation prior to intrauterine insemination?

OBJECTIVE

To compare the efficacy of letrozole with clomiphene citrate for ovarian stimulation prior to intrauterine insemination.

METHODS

A total of 272 patients underwent 362 cycles of stimulation prior to IUI from January 2009 to May 2011. One hundred and twenty-six patients (170 cycles) received letrozole 5 mg and 146 patients (192 cycles) received clomiphene citrate 100 mg for 5 days starting on day 3 of the cycle. Intrauterine insemination was done 36 ± 4 h after hCG injection in 99 patients (131 cycles) in the letrozole group and 115 patients (136 cycles) in the clomiphene group. The number of mature follicles and serum E2 levels was monitored on the day of hCG. Endometrial thickness was noted on the day of hCG and IUI as well. The pregnancy rate, the miscarriage rate, and other parameters were evaluated only for patients who underwent IUI.

RESULTS

The mean number of mature follicles was significantly more in the clomiphene group (1.66 ± 1.69 vs. 1.41 ± 1.53) than in the letrozole group. No significant difference in endometrial thickness on the day of hCG administration was found; however, endometrial thickness was statistically significantly higher in the clomiphene group on the day of IUI (9.28 ± 1.43 vs. 8.77 ± 1.34). Serum E(2) levels on the day of hCG were statistically significantly higher in the clomiphene group (501.09 ± 2.45 vs. 214.79 ± 2.43 pg/ml). Pregnancy rate was 9.2 %/cycle and 12.12 %/patient in the letrozole group, and 8.1 %/cycle and 9.5 %/cycle in the clomiphene group; these differences were not statistically significant.

CONCLUSION

This study found no superiority of letrozole over clomiphene when used for ovarian stimulation and IUI.

Clomiphene citrate or letrozole as first-line ovulation induction drug in infertile PCOS women: A prospective randomized trial

OBJECTIVE

To compare Letrozole (5 mg) and clomiphene citrate (100 mg) as first line ovulation induction drug in infertile PCOS women.

STUDY DESIGN

Prospective Randomised trial.

SETTING

A Tertiary level infertility centre.

PATIENTS

103 infertile PCOS women.

INTERVENTIONS

Treatment naïve infertile PCOS women were randomised to treatment with 5 mg letrozole (51 patients) or 100 mg clomiphene citrate (52 patients) daily starting day 2 to day 6 of menstrual cycle. Timed intercourse or Intra Uterine Insemination (IUI) was advised 24 to 36 hours after Human Chorionic Gonadotropin (HCG) injection.

MAIN OUTCOME MEASURES

Ovulation rate, mono or multi follicular rate, days to ovulation, endometrial thickness, serum progesterone, serum estrogen, pregnancy rate, miscarriage rate.

RESULTS

The mean age, Body Mass Index (BMI), duration of infertility in both Clomiphene Citrate (CC) and Letrozole groups were similar.Ovulation rate was 73.08% in letrozole group and 60.78% in CC, which was not statistically significant (P=0.398). There was no statistically significant difference between Endometrial thickness (CC 7.61 ±1.96, Let 7.65 ± 2.10), Sr E2 on day of HCG (CC 178.3 ± 94.15, Let 162.09 ± 73.24), Days to ovulation (CC 14.2 ± 3.41; Let 13.13 ± 2.99) and Sr P4 on D21 (CC 10.58 ± 6.65; Let 11.86 ± 6.51). Monofolliculo genesis (CC 54.84, Let 79.49 %, P=0.027) and Pregnancy rate (CC 7.84%, Let 21.56% P=0.0125) were statistically significantly higher in letrozole group.

CONCLUSION

Our study shows that letrozole has excellent pregnancy rates compared to clomiphene citrate. Letrozole should be considered at par with clomiphene citrate as first line drug for ovulation induction in infertile PCOS women.

A prospective randomized trial comparing the efficacy of Letrozole and Clomiphene citrate in induction of ovulation in polycystic ovarian syndrome

OBJECTIVES:

To compare the efficacy of letrozole and clomiphene citrate (CC) in patients of anovulatory polycystic ovarian syndrome (PCOS) with infertility.

MATERIALS AND METHODS:

This prospective randomized clinical trial included 204 patients of PCOS. 98 patients (294 cycles) received 2.5–5 mg of letrozole; 106 patients (318 cycles) received 50–100 mg of CC (both orally from Days 3–7 of menstrual cycle). The treatment continued for three cycles in both the groups. Main outcome measures: ovulation rate, endometrial thickness, and pregnancy rate. Statistical analysis was done using SPSS 13 software. P value less than 0.05 was considered significant.

RESULTS:

The mean number of dominant follicles in letrozole groups and CC groups was 1.86±0.26 and 1.92±0.17, respectively (P=0.126). Number of ovulatory cycle in letrozole group was 196 (66.6%) versus 216 (67.9%) in CC group (P=0.712). The mean mid-cycle endometrial thickness was 9.1±0.3 mm in letrozole group and 6.3±1.1 in CC group, which was statistically significant (P=0.014). The mean Estradiol [E2] level in clomiphene citrate group was significantly higher in CC group (364.2±71.4 pg/mL) than letrozole group (248.2± 42.2 pg/mL). 43 patients from the letrozole group (43.8%) and 28 patients from the CC group (26.4%) became pregnant.

CONCLUSION:

Letrozole and CC have comparable ovulation rate. The effect of letrozole showed a better endometrial response and pregnancy rate compared with CC.

Ovarian stimulation and intrauterine insemination at the quarter centennial: implications for the multiple births epidemic

Ovarian stimulation and intrauterine insemination (OS/IUI), a mainstay of current infertility therapy and a common antecedent to IVF, is a significant driver of the multiple births epidemic. Redress of this challenge, now marking its quarter centennial, will require a rethinking of current practice patterns. Herein we explore prospects for prevention, mitigation, and eventual resolution. We conclude that the multiple births attributable to OS/IUI may not be entirely preventable but that the outlook for their mitigation is promising, if in need of solidification. Specifically, we observe that low-dose (≤ 75 IU) gondotropin, clomiphene, and especially off-label letrozole regimens outperform high-dose (≥ 150 IU) gonadotropin counterparts in the gestational plurality category while maintaining comparable per-cycle pregnancy rates. Accordingly we recommend that, subject to appropriate exceptions, high-dose gonadotropin regimens be used sparingly and that whenever possible they be replaced with emerging alternatives. Finally, we posit that OS/IUI is not likely to be superseded by IVF absent further commoditization and thus greater affordability.

Randomized comparison of superovulation with letrozole vs. clomiphene citrate in an IUI program for women with recently surgically treated minimal to mild endometriosis

OBJECTIVE

To evaluate pregnancy rates with letrozole and clomiphene citrate (CC) alone for superovulation in an intrauterine insemination program for women with recently surgically treated minimal to mild endometriosis.

DESIGN

A randomized controlled trial following the CONSORT criteria.

SETTING

University teaching hospital and a private practice setting.

PATIENTS

136 women with primary infertility due to minimal to mild endometriosis who did not achieve pregnancy after six to 12 months following laparoscopic treatment.

INTERVENTIONS

Superovulation using 5 mg letrozole/day (69 women, 220 cycles) or 100 mg CC/day (67 women, 213 cycles) for five days combined with intrauterine insemination up to four cycles.

MAIN OUTCOME MEASURES

Clinical pregnancy rate per cycle, cumulative pregnancy rate after four cycles, number of follicles, serum estradiol, endometrial thickness on the day of human chorionic gonadotropin administration, serum progesterone, miscarriage and live birth rates.

RESULTS

The clinical pregnancy rate per cycle and the cumulative pregnancy rate after four cycles were comparable (15.9 vs. 14.5% and 64.7 vs. 57.2%; p=0.82, p=0.71 in letrozole and CC groups, respectively). Two twin pregnancies occurred in the CC/intrauterine insemination group. Miscarriage and live birth rates were comparable (11.4 vs. 12.9% and 44.9 vs. 40.3%; p=0.47, p=0.62 in letrozole and CC groups, respectively). The total number of follicles and serum estradiol on the day of human chorionic gonadotropin administration were significantly increased in the CC group.

CONCLUSIONS

Superovulation with letrozole is not more effective than clomiphene citrate alone in an intrauterine insemination program for women with minimal to mild endometriosis who did not achieve pregnancy after six to 12 months following laparoscopic treatment. ClinicalTrials.gov ID: NCT01334762.

The Pregnancy in Polycystic Ovary Syndrome II (PPCOS II) trial: rationale and design of a double-blind randomized trial of clomiphene citrate and letrozole for the treatment of infertility in women with polycystic ovary syndrome

Polycystic Ovary Syndrome (PCOS) is a common cause of female infertility and first line treatment is currently oral clomiphene citrate, a selective estrogen receptor modulator, which results in both a high nonresponse rate and multiple pregnancy rate. Aromatase inhibitors such as letrozole may have more favorable ovarian and endometrial effects. The goal of the Pregnancy in Polycystic Ovary Syndrome II (PPCOSII) study is to determine the safety and efficacy of clomiphene citrate (CC) compared to letrozole, in achieving live birth in infertile women with PCOS. The population will consist of 750 infertile women with PCOS. Additionally, the couple will have no other major infertility factor. This will be a multi-center, prospective, double-blind clinical trial of CC vs. letrozole for 5 treatment cycles (or approximately up to 25 weeks). The randomization scheme will be coordinated through the central data coordinating center (DCC) and the randomization is stratified by each participating site. After progestin withdrawal as needed, 750 women will be equally randomized to two different treatment arms: A) CC 50mg every day for 5 days (days 3-7 of cycle), or B) letrozole 2.5mg every day for 5 days (days 3-7 of cycle), for a total of 5 cycles or 25 weeks. The dose will be increased in subsequent cycles in both treatment groups for non-response or poor ovulatory response up to a maximum of 150 mg of CC a day (×5 days) or 7.5mg of letrozole a day (×5 days). The primary analysis will use an intent-to-treat approach to examine differences in the live birth rate in the two treatment arms.

Effects of a non-steroidal aromatase inhibitor on ovarian function in cattle

Effects of the non-steroidal aromatase inhibitor letrozole on ovarian function in cattle were determined. The hypothesis that letrozole would arrest growth of the dominant follicle, resulting in emergence of a new follicular wave at a predictable post-treatment interval, was tested. Heifers were assigned randomly to four groups 4 days after follicular ablation (~2½ days after wave emergence) and given intravenous doses of 500 (n = 9), 250 (n = 10), or 125 µg kg–1 (n = 10) letrozole or phosphate-buffered saline (controls; n = 10). Blood was collected and ovarian structures were monitored daily by transrectal ultrasonography. Plasma concentrations of LH and FSH were measured by radioimmunoassay; plasma concentrations of letrozole were determined by high-performance liquid chromatography tandem mass spectrometry. A single intravenous dose of letrozole did not induce regression of the dominant follicle present at the time of treatment, nor did it directly affect FSH release. Conversely, treatment with letrozole increased endogenous concentrations of LH and extended the lifespan of the dominant follicle, which delayed the next FSH surge and subsequent follicular wave emergence. Letrozole continues to have potential as a non-steroidal treatment for controlling ovarian function in cattle.

Estimating rates of multiple gestation pregnancies: sample size calculation from the assessment of multiple intrauterine gestations from ovarian stimulation (AMIGOS) trial

Infertility afflicts 15% of couples who wish to conceive. Despite intensive evaluation of both male and female partners, the etiology may remain unknown leading to a diagnosis of unexplained infertility. For such couples, treatment often entails ovulation induction (OI) with fertility medications coupled with intrauterine insemination. Complications of this therapy include ovarian hyperstimulation syndrome and creation of multiple gestation pregnancies, which can be complicated by preterm labor and delivery, and the associated neonatal morbidity and expense of care for preterm infants. The Assessment of Multiple Intrauterine Gestations from Ovarian Stimulation (AMIGOS) study is designed to assess whether OI in couples with unexplained infertility with an aromatase inhibitor produces mono-follicular development in most cycles, thereby reducing multiple gestations while maintaining a comparable pregnancy success rate to that achieved by OI with either gonadotropins or clomiphene citrate. These results will provide future guidance of therapy for couples with unexplained infertility, and if comparable pregnancy rates are achieved with a substantial reduction in multiple gestations, the public health benefit will be considerable.

Hormonal, follicular and endometrial dynamics in letrozole-treated versus natural cycles in patients undergoing controlled ovarian stimulation

The objective of this study was to compare letrozole-stimulated cycles to natural cycles in 208 patients undergoing intrauterine insemination (IUI) between July of 2004 and January of 2007. Group I (n = 47) received cycle monitoring only (natural group), Group II (n = 125) received letrozole 2.5 mg/day on cycle days three to seven, and Group III (n = 36) received letrozole 5 mg/day on cycle days three to seven. There were no differences between the groups in endometrial thickness or P₄ on the day of hCG. Estradiol levels had higher variation in the second half of the follicular phase in both letrozole-treated groups compared to the control group. Estradiol per preovulatory follicle was similar in both letrozole cycles to that observed in the natural cycles. LH was lower on the day of hCG administration in the letrozole 2.5 mg/day group vs. the natural group. In summary, letrozole results in some minor changes in follicular, hormonal and endometrial dynamics compared to natural cycles. Increased folliculogenesis and pregnancy rates were observed in the letrozole-treated groups compared to the natural group. These findings need to be confirmed in larger, prospective studies.

Aromatase inhibitors for ovulation induction and ovarian stimulation

Aromatase inhibitors (AIs) were originally developed for the treatment of advanced breast cancer in postmenopausal women. Their use in reproductive medicine has been extensively studied in the past decade. We reviewed the current strategies for ovulation induction for anovulatory women, mostly women with polycystic ovarian syndrome (PCOS), and the scientific basis for use of AIs in reproductive medicine. The AI, letrozole, is effective in ovulation induction in women with PCOS resistant to clomifene citrate and ovarian stimulation for intrauterine insemination and in vitro fertilization (IVF). Letrozole is an attractive option with its oral route of administration, cost, safety profile and effectiveness in ovulation induction and ovarian stimulation. Letrozole has the potential to be the first-line treatment option for ovulation induction in PCOS women, while its use in ovarian stimulation for IVF deserves further study.

Letrozole for ovulation induction and controlled ovarian hyperstimulation

PURPOSE OF REVIEW

Letrozole, an aromatase inhibitor, is the newest addition to our armamentarium in the treatment of infertility. It is utilized in much the same way as clomiphene citrate, but with some additional benefits. In this review, the latest studies will be summarized with emphasis on dose, duration of use, safety, number of mature follicles, and pregnancy outcomes.

RECENT FINDINGS

Letrozole has fewer side effects, and a shorter half-life than clomiphene citrate, and no demonstrable effect upon the receptivity of the endometrium. It is efficacious in treating women with chronic anovulation, unexplained infertility and diminished ovarian reserve. Its safety is superior to clomiphene citrate. Utilizing bio-equivalent doses, letrozole pregnancy rates are equal or superior to clomiphene citrate. Several studies suggest situations where it is more efficacious than gonadotropin treatment.

SUMMARY

With further study, this drug could replace clomiphene citrate as the primary medication for chronic anovulation and/or unexplained infertility. It could augment or even obviate the use of gonadotropins in the treatment of women who have been unsuccessful in achieving pregnancy with clomiphene citrate. It may also be an adjunct for women with diminished ovarian reserve. Further studies are needed to determine optimal dosing and long term safety for women treated with the drug.

Aromatase inhibitors for female infertility: a systematic review of the literature

Ovulation induction remains a milestone in the treatment of women with anovulatory infertility. Clomiphene citrate (CC) is considered the first line treatment for induction of ovulation in women with polycystic ovary syndrome (PCOS), while it may be used for ovulation induction in unexplained infertility. Aromatase inhibitors (AI) have been introduced as a new treatment option that could challenge CC for ovulation induction. A systematic review of the literature was conducted in order to highlight the efficacy and safety of AI in female infertility. Current data from randomized and non-randomized trials suggest that AI may have a role in ovulation induction regimens in PCOS patients, as well as for ovarian stimulation, since they achieve comparable clinical pregnancy rates to CC. Furthermore, when combined with gonadotrophins, AI improve the ovarian response of poor responders and reduce the gonadotrophin dose required. However, the current review is based on small trials with a limited number of patients. If solid data from future large adequately powered randomized trials support current evidence regarding efficacy and safety, AI might offer a new treatment choice for infertile women.

Clomiphene citrate or anastrozole for ovulation induction in women with polycystic ovary syndrome? A prospective controlled trial

OBJECTIVE

To compare the effects of anastrozole (1 mg) and clomiphene citrate (CC; 100 mg) used for ovulation induction in women with polycystic ovary syndrome.

DESIGN

Prospective controlled trial.

SETTING

University teaching hospital and private-practice setting.

PATIENT(S)

The study comprised a total of 216 infertile women (469 cycles) with polycystic ovary syndrome.

INTERVENTION(S)

Patients received anastrozole (1 mg/d; 115 patients, 243 cycles) for 5 days, starting on day 3 of menses. A matched historical group of patients with polycystic ovary syndrome who were treated with CC (100 mg/d; 101 patients, 226 cycles) was used as a control group. Timed intercourse was advised 24-36 hours after hCG injection.

MAIN OUTCOME MEASURE(S)

Number of follicles, serum E(2), serum P, endometrial thickness, and pregnancy and miscarriage rates.

RESULT(S)

The mean age, parity, and duration of infertility in both groups were similar, but statistically significantly more polycystic ovaries were found in the anastrozole group (odds ratio = 2.44; 95% confidence interval = 1.19-5.02). The total numbers of follicles were significantly higher in the CC group (3.8 +/- 0.6 vs. 3.4 +/- 0.5). Endometrial thickness at the time of hCG administration was significantly greater in the anastrozole group (10.1 +/- 0.22 mm vs. 8.2 +/- 0.69 mm). The duration of stimulation was similar in the two groups. Ovulation occurred in 165 (67.9%) of 243 cycles in the anastrozole group and in 150 (68.6%) of 226 cycles in the CC group without significant difference. Serum P was significantly higher in the CC group (7.1 +/- 1.11 vs. 8.1 +/- 0.88 ng/mL). The pregnancy and miscarriage rates were similar in the two groups.

CONCLUSION(S)

Anastrozole was associated with significantly fewer mature and growing follicles, thicker endometrium, and slightly higher pregnancy rate. Anastrozole may be helpful in situations in which multiple pregnancy is not desirable or the risk of ovarian hyperstimulation syndrome is high.

Comparison of letrozole with continuous gonadotropins and clomiphene-gonadotropin combination for ovulation induction in 1387 PCOS women after clomiphene citrate failure: a randomized prospective clinical trial

PURPOSE

Letrozole, though reported to be an effective ovulation inducing agent, warrants larger randomized trials. The purpose of this study is to compare the efficacy of letrozole with that of rFSH and clomiphene citrate(CC)/rFSH for ovarian stimulation in IUI cycles.

METHODS

Randomized, prospective, single-blinded clinical trial. 1387 PCOS women after CC failure were randomized into three groups: Group A received letrozole, Group B received CC with two doses rFSH and Group C received continuous rFSH day 2 onwards until hCG injection.

RESULTS

Group A, B and C had an ovulation rate of 79.30%, 56.95% and 89.89% and cycle cancellation rate of 20.70%, 43.05% and 10.11%, respectively. Pregnancy rates in Group A, B and C were 23.39%, 14.35% and 17.92%, while the miscarriage rates were 13.80%, 16.67% and 14.52%, respectively.

CONCLUSION

Letrozole appears to be a suitable ovulation inducing agent in PCOS women with CC failure and is found to be most effective when baseline estradiol level >60 pg/ml.

Use of letrozole in assisted reproduction: a systematic review and meta-analysis

BACKGROUND

Letrozole is the third-generation aromatase inhibitor (AI) most widely used in assisted reproduction. AIs induce ovulation by inhibiting estrogen production; the consequent hypoestrogenic state increases GnRH release and pituitary follicle-stimulating hormone (FSH) synthesis.

METHODS

A systematic search of the literature was performed for both prospective and retrospective studies. Meta-analyses of randomized clinical trials (RCTs) were performed for three comparisons: letrozole versus clomiphene citrate (CC), letrozole + FSH versus FSH in intrauterine insemination (IUI) and letrozole + FSH versus FSH in IVF. In the absence of RCTs, non-randomized studies were pooled.

RESULTS

Nine studies were included in the meta-analysis. Four RCTs compared the overall effect of letrozole with CC in patients with polycystic ovary syndrome. The pooled result was not significant for ovulatory cycles (OR = 1.17; 95% CI 0.66–2.09), or for pregnancy rate per cycle (OR = 1.47; 95% CI 0.73–2.96) or for pregnancy rate per patient (OR = 1.37; 95% CI 0.70–2.71). In three retrospective studies which compared L + FSH with FSH in ovarian stimulation for IUI, the pooled OR was 1.15 (95% CI 0.78−1.71). A final meta-analysis included one RCT and one cohort study that compared letrozole + gonadotrophin versus gonadotrophin alone: the pooled pregnancy rate per patient was not significantly different (OR = 1.40; 95% CI 0.67–2.91).

CONCLUSIONS

Letrozole is as effective as other methods of ovulation induction. Further randomized-controlled studies are warranted to define more clearly the efficacy and safety of letrozole in human reproduction.

RETRACTED: Anastrozole or letrozole for ovulation induction in clomiphene-resistant women with polycystic ovarian syndrome: a prospective randomized trial

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the ASRM Publications Committee. Several reports of randomized clinical trials were recently the subject of an investigation conducted by the publications committee of the ASRM. The committee reviewed concerns related to the validity of data reported in those reports. The committee noted significant duplication of data reported in this manuscript with data reported in another report (PMID: 19732888; https://doi.org/10.1016/j.fertnstert.2009.07.985) pertaining to a different study group that could not be explained. As we cannot vouch for the validity of the data, we have issued a retraction of this paper.

A comparison of the effects of clomiphene citrate and the aromatase inhibitor letrozole on superovulation in Asian women with normal ovulatory cycles

OBJECTIVE

To compare the effect of the aromatase inhibitor letrozole and clomiphene citrate (CC) on superovulation in women with normal ovulation.

METHODS

A cross-over randomized study of 22 women with normal ovulation, divided randomly into two equal cohorts, was carried out. Each group of 11 women was randomly allocated to take letrozole or CC for one cycle. After washing out for one cycle, the alternative drug was administered in the subsequent cycle. The number and size of mature follicles, endometrial thickness, and estradiol and progesterone levels were monitored.

RESULTS

The number of mature follicles and estradiol levels on ovulation day were significantly lower in the letrozole group than the CC group (p < 0.05 for both). However, no differences between the two groups in endometrial thickness and pattern were observed. Progesterone levels showed ovulation in all cycles.

CONCLUSIONS

The administration of 50 mg CC on days 3-5 was superior to 2.5 mg letrozole for superovulation induction in women with normal ovulation.

RETRACTED: Clomiphene citrate or letrozole for ovulation induction in women with polycystic ovarian syndrome: a prospective randomized trial

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the ASRM Publications Committee Several reports of randomized clinical trials were recently the subject of an investigation conducted by the publications committee of the ASRM. The committee reviewed concerns related to the validity of data reported in those reports. The committee noted significant duplication of data reported in this manuscript with data reported in another journal (PMID 17364286; https://doi.org/10.1080/00016340601090337) and another publication in Fertility and Sterility (PMID: 18692823; https://doi.org/10.1016/j.fertnstert.2008.06.013) pertaining to different study groups that could not be explained. As we cannot vouch for the validity of the data, we have issued a retraction of this paper.

New advances in ovulation induction

PURPOSE OF REVIEW

To review recent advances in ovulation induction.

RECENT FINDINGS

Aromatase inhibitors can replace clomiphene citrate as ovulation-inducing substances. The most widely used aromatase inhibitor for this purpose is letrozole and the optimal dose is 5 mg daily for 5 days. Compared to clomiphene citrate, it is associated with a thicker endometrium and a better pregnancy rate. It is as effective as gonadotropin but yet less expensive. The overall rates of congenital malformation among newborns conceived after infertility treatment with letrozole or clomiphene citrate are similar. When letrozole is combined with gonadotropin, it leads to lower gonadotropin requirements with pregnancy rates comparable to gonadotropin treatment alone. Another promising aromatase inhibitor is anastrazole. Recent evidence suggests that luteinizing hormone activity in human menopausal gonadotropin modifies follicular development so that fewer intermediate-sized follicles develop. Compared to the use of follicular stimulating hormone only, human menopausal gonadotropin is associated with less ovarian hyperstimulation.

SUMMARY

Aromatase inhibitors are alternative drugs to clomiphene or gonadotropin for ovulation induction or superovulation.