Randomized controlled trial of three doses of letrozole for ovulation induction in patients with unexplained 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.

Live birth associated with peak serum estradiol levels in letrozole intrauterine insemination cycles

OBJECTIVE

To identify whether the serum estradiol (E2) level on the day of human chorionic gonadotropin (hCG) trigger or luteinizing hormone (LH) surge (hCG-LH) was associated with the live birth rate (LBR) during ovulation induction (OI) or controlled ovarian hyperstimulation with letrozole followed by intrauterine insemination (IUI).

DESIGN

Retrospective cohort study.

SETTING

Large, multicenter private practice.

PATIENT(S)

A total of 2,368 OI-IUI cycles in patients treated with letrozole followed by IUI were evaluated from January 1, 2014, to July 31, 2019.

INTERVENTION(S)

Ovulation induction with letrozole, followed by autologous IUI.

MAIN OUTCOME MEASURE(S)

The primary outcome measure was the LBR as a function of the serum E2 level at the time of hCG administration or LH surge, adjusting for age, body mass index, the largest follicle diameter, and the number of follicles ≥14 mm in diameter. The clinical pregnancy rate as a function of the E2 level, pregnancy rate as a function of the lead follicle diameter, and pregnancy loss rates were the secondary outcome variables.

RESULT(S)

A total of 2,368 cycles met the inclusion criteria. Outcomes were evaluated at the 25th (E2 level, 110 pg/mL), 50th (157 pg/mL), 75th (225 pg/mL), and 90th (319 pg/mL) percentiles. The LBRs ranged from 9.4% to 11.1% in the lower E2 cohorts and from 12.5% to 13.5% in the higher E2 cohorts. The LBR was significantly greater in the cohort of women with higher E2 levels in all percentile comparisons except for the 90th percentile. The mean periovulatory follicle diameter of ≥20 or <20 mm was not independently associated with the LBR or clinical pregnancy rate, despite a significantly higher mean E2 level in the larger follicle group.

CONCLUSION(S)

In letrozole OI cycles followed by IUI, lower LBRs and clinical pregnancy rates were found in women with lower E2 levels than in those with higher E2 levels at the 25th, 50th, and 75th percentile E2 level quartiles. Where possible, delaying hCG trigger until the E2 level increases after aromatase inhibition and approaches the physiologic periovulatory level may improve the pregnancy rates with letrozole followed by IUI.

Effect of different timing of letrozole initiation on pregnancy outcome in polycystic ovary syndrome

OBJECTIVE

To investigate the efficacy of oral letrozole (LE) starting on day 3 or 5 of the menstrual cycle in patients with polycystic ovary syndrome (PCOS).

DESIGN

Retrospective cohort study.

SETTING

Reproductive Endocrinology Department of Hangzhou Women's Hospital.

METHODS

In this retrospective analysis, we analyzed patients who received oral LE for ovulation induction (OI) at the Hangzhou Women's Hospital from January 2016 to January 2021. In total, 539 PCOS patients with fertility requirements were classified into the D3 group and D5 group according to the different starting times of oral LE, that is, from the 3rd or 5th day of the menstrual cycle or LE is taken orally for 5 days starting on day 3 or 5 of progesterone withdrawal bleeding. Treatment started with one tablet (LE 2.5 mg), continue the regimen from the previous cycle in non-responders and continued until pregnancy or for up to three ovulatory cycles, with visits to determine ovulation and pregnancy, followed by tracking of pregnancies. The primary outcome was to compare ovulation rates, conception rates, live birth rates, pregnancy complications, and pregnancy outcomes at different initiation times.

RESULTS

Women who started LE on the 5th day of their menstrual cycle had more cumulative conception rates than those who started LE on the 3rd day(173 of 228[75.9%]vs. 201 of 311[64.6%], P= 0.005; rate ratio for conception, 1.174; 95% confidence interval,1.052 to 1.311) without significant differences in overall live birth rate, though there were 142 of 228[62.3%] in the D5 group versus 172 of 311[55.3%] in the D3 group (P= 0.105). The median (IQR) endometrial thickness was significantly (P = 0.013) greater during the D5 group treatment compared to the D3 group, which may be related to higher conception and clinical pregnancy rates. The median (IQR) maximum follicle diameter was not statistically (P = 0.073) different between the two groups. The cumulative ovulation per cycle rate was higher with D5 than with D3 (287 of 405 treatment cycles [70.9%] vs. 388 of 640 treatment cycles [60.6%], P=0.001). There were no significant between-group differences in pregnancy loss (31 of 173 conceptions in the D5 group [17.9%] and 29 of 201 conceptions in the D3 group [14.4%]) or multiples pregnancy (8.2% and 10.5%, respectively). Rates of other adverse events during pregnancy were similar in the two treatment groups.

CONCLUSION

As compared with D3 group, D5 group was associated with higher ovulation and conception rates, shorter time-to-pregnancy among infertile women with the PCOS.

Effects of using letrozole in combination with the GnRH antagonist protocol for patients with poor ovarian response: A meta-analysis

This meta-analysis aimed to compare the outcomes of the gonadotrophin-releasing hormone (GnRH) antagonist/letrozole protocol with those of the conventional GnRH antagonist protocol for poor responders undergoing in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI). We searched for relevant articles in PubMed, EMBASE, Google Scholar, and retrieved 452 records. Eventually, we selected five eligible trials with data for 564 patients characterized as poor ovarian responders. Our meta-analysis revealed that the clinical pregnancy rate (per cycle) with administration of letrozole might be a higher than that in the control groups (risk rate [RR]: 1.57, 95% confidence interval [CI]: 1.00-2.44, p = 0.05). .Moreover,it indicated that the total dose of gonadotrophin was significantly decreased with the administration of letrozole compared to control groups(mean difference [MD]: -529.37, 95% CI: -1207.45 to -111.25, p = 0.001),.However, there was no statistical difference in the number of retrieved oocytes(MD: 0.59, 95% CI: -0.36-1.54, p = 0.22), cycle cancelation rate (RR: 0.81, 95% CI: 0.58-1.12, p = 0.20), or estradiol concentration on the day of HCG administration(MD: -28.19, 95% CI: -77.71-21.33, p = 0.26) in the presence or absence of letrozole combination in the GnRH antagonist protocol. In conclusion, letrozole administration might improve clinical pregnancy rate in conventional GnRH antagonist protocol for poor responders. Moreover, letrozole co-treatment aslo can reduce the economic burden of poor responders during the GnRH antagonist cycle. Nevertheless, large-scale and multi-center randomized controlled trials are needed to further evaluate the efficacy of adjunctive letrozole administration in the GnRH antagonist protocol.

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.

Comparison of clomiphene and letrozole for superovulation in patients with unexplained infertility undergoing intrauterine insemination: A systematic review and meta-analysis

BACKGROUND

With the medical advancement some studies put forward that letrozole (LE), a specific aromatase inhibitor with the function of reducing oestrogen synthesis, has recently been applied as a potentially better alternative compared with clomiphene citrate (CC), owing to that it has a superior efficacy as compared with CC in patients of unexplained infertility undergoing intrauterine insemination (IUI). However, there is no one study can clear and definite whether LE can replace the CC as first line drug.

OBJECTIVE

Our objective is to compare the LE with CC in the induction of ovulation in patients with unexplained infertility IUI.

METHOD

Searching databases consist of all kinds of searching tools, such as Medline, The Cochrane Library, Embase, PubMed, etc. All the include studies should meet our demand of this meta-analysis: RESULT:: Based on the current meta-analysis, we rigorously consider that LE has a likelihood to improve dominant follicles (MD= -0.56, I= 100%, P= .04; MD= -0.39, I= 73%, P = .0003, respectively) and reduces the miscarriage rate (RR= 0.61, I= 0%, P = .03). There is no significant differences between the 2 groups in The total rate of pregnancy, pregnancy rate per cycle, multiple pregnancy and endometrial thickness. (RR= 1.06, I= 11%, P = .38; RR= 1.09, I= 7%, P = .32; RR= 0.79, I= 0%, P = .46; respectively) CONCLUSION:: Combined with the results of current systematic review and meta-analysis through subgroup analysis and sensitivity analysis, we can be cautious: in general, compared with CC, LE is an effective treatment in the IUI cycle, has a likelihood to improve dominant follicles and reduces the miscarriage rate.

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.

Letrozole and human menopausal gonadotropin for ovulation induction in clomiphene resistance polycystic ovary syndrome patients: A randomized controlled study

OBJECTIVE

To compare the effects of letrozole and human menopausal gonadotropin (HMG) in the treatment of patients with polycystic ovary syndrome (PCOS) resistant to clomiphene citrate (CC).

METHODS

A total of 96 clomiphene resistance polycystic ovary syndrome patients infertility were randomly divided into an LE group, and HMG group (n = 48). LE group orally received letrozole at 5.0 mg/d on the 3rd-5th days of menstrual cycle for 5 consecutive days, and 75 U/d HMG was given through intramuscular injection for 5 days starting from the third day of menstrual cycle in HMG group. Number of growing and mature follicles, serum E2 (pg/mL), serum P (ng/mL), endometrial thickness, occurrence of pregnancy and miscarriage were observed.

RESULTS

There was no significant difference in the number of ovulation cycles between the 2 groups (53.6% vs 64.7%, P > .05). The number of mature follicular cycles in the HMG group was higher than that of the letrozole group (P < .01). There were no significant differences in the clinical pregnancy rate (22.9% vs 27.1%, P > .05) and abortion rate (6.2% vs 10.4%, P > .05). There was no significant difference in the endometrial thickness between the 2 groups on the day of HCG injection [(9.1 ± 0.2) mm vs (10.7 ± 1.6) mm, P > .05]; the serum estradiol (E2) was lower in the letrozole group. The incidence of ovarian cysts was lower than that of HMG group (P < .05). There was2 ovarian hyperstimulation syndrome in the letrozole group; the incidence of ovarian hyperstimulation syndrome in the HMG group was 12.5%.

CONCLUSION

Letrozole-induced ovulation can obtain ovulation rate and pregnancy rate similar to gonadotropin, but reduce the risk associated with treatment. It can be used as an effective ovulation option for patients with polycystic ovary syndrome who are resistant to clomiphene.

Effects of a single 20 mg dose of letrozole on ovarian function post dominant follicle selection: an exploratory randomized controlled trial

BACKGROUND

Our objective was to explore the impact of a single dose of an aromatase inhibitor (letrozole) administered at defined times of the follicular phase or immediately after ovulation on dominant follicle development, luteogenesis and new follicle wave emergence.

METHODS

A prospective pilot study using a randomized complete block, controlled, open label design was conducted at an academic clinical research center. Forty-five healthy, female volunteers (25.5 ± 0.9 years, BMI 25.0 ± 0.6 kg/m2) who had not taken hormonal contraceptives for a minimum of 2 months were recruited. A 20 mg dose of Letrozole was administered once orally in each of 3 groups when the dominant follicle reached a diameter of 1) 12 mm, 2) 18 mm, 3) the first day following ovulation (post-ovulation), or 4) treatment was withheld (control). Serial ultrasonography and phlebotomy began on day 4 of the menstrual cycle and continued for 1.5 menstrual cycles. Participants recorded menses and daily events in a life events calendar for the duration of the study. Demographic and single point measurements were compared among groups by ANOVA. Changes in hormone concentrations over time were compared among groups by repeated measures ANOVA. Kruskal-Wallis tests were used for non-normally distributed data.

RESULTS

The dominant follicle in all treatment groups ovulated. There were no differences among experimental groups in peak follicle diameter, follicular growth rate, endometrial thickness at ovulation or inter-ovulatory interval. Plasma concentrations of estradiol dropped, while FSH and LH concentrations rose following treatment in all treatment groups. Plasma FSH and LH concentrations were higher in the 18 mm group compared to the 12 mm and post-ovulation groups (P < 0.02).

CONCLUSION

Administration of a single 20 mg dose of Letrozole at the times of the menstrual cycle we examined did not induce dominant follicle regression or failure of corpus luteum formation. Letrozole-induced suppression of estradiol synthesis by the dominant follicle was not detrimental to follicle growth or ovulation following follicle selection, likely due to increased circulating concentrations of FSH and LH resulting from a lack of estradiol-induced suppression of the hypothalamic-pituitary-ovarian axis.

TRIALS REGISTRATION NUMBER

Clinical trials registration number NCT01046578 .

Use of aromatase inhibitors in practice of gynecology

Purpose

The conversion of androgens into estrogens by aromatase is called aromatization and is inhibited by aromatase inhibitors (AIs). The aim of this article is to evaluate the use of aromatase inhibitors in gynecological diseases such as endometriosis, leiomyoma, estrogen- dependent gynecologic neoplasia and infertility.

Methods

This is a review of literature combined with experience and use of aromatase ınhıbıtors ın practıce of gynecology.

Conclusion

AIs are promising agents in treatment of estrogen dependent disease. However lack of experience, side effects and cost are limiting factors for using these agents in infertility treatment. However there is need for larger, well designed randomized trials to generate robust data in order to establish the true potential of aromatase inhibitors.

First reported case of sextuplets conceived via letrozole for ovulation induction

OBJECTIVE

To report the first case of sextuplets conceived via letrozole during ovulation induction.

DESIGN

Case report.

SETTING

Private fertility clinic.

PATIENT(S)

A 32-year-old female with a history of secondary infertility and polycystic ovary syndrome.

INTERVENTION(S)

Letrozole, 7.5 mg, on cycle days 3-7 after a progesterone-induced menses.

MAIN OUTCOME MEASURE(S)

Clinical pregnancy.

RESULT(S)

Sexchorionic-sexamniotic pregnancy.

CONCLUSION(S)

High-order multiple gestations are possible with letrozole ovulation induction, so patients should be counseled appropriately and follicle monitoring considered.

Minimal stimulation protocol using letrozole versus microdose flare up GnRH agonist protocol in women with poor ovarian response undergoing ICSI

BACKGROUND

To compare the IVF outcomes of letrozole/antagonist and microdose GnRH agonist flare up protocols in poor ovarian responders undergoing intracytoplasmic sperm injection.

MATERIALS AND METHODS

A randomized controlled trial was performed in patients with one or more previous failed IVF cycles in which four or less oocytes were retrieved when the gonadotrophin starting dose was at least 300 IU/day. Sixty patients were randomized by computer-generated list to receive either letrozole/antagonist (mild stimulation) n = 30 or GnRH-a protocol (microdose flare) n = 30.

RESULTS

Both groups were similar with respect to background and hormonal characteristics (age, duration of infertility, BMI, FSH, LH and E2). The clinical pregnancy rate per cycle was similar in both groups (13.3 vs. 16.6%; OR = 0.769; 95% CI = 0.185, 3.198). The doses of used gonadotropins and the number of stimulation days were significantly lower in the letrozole/antagonist protocol. The peak E2 level on the day of hCG, the endometrial thickness, the retrieved oocytes, the number of fertilized oocytes, the number of transferred embryos and the cancellation rate were statistically similar in both groups.

CONCLUSIONS

The letrozole/antagonist protocol is a cost-effective and patient-friendly protocol that may be used in poor ovarian responders for IVF/ICSI.

Extended high dose letrozole regimen versus short low dose letrozole regimen as an adjuvant to gonadotropin releasing hormone antagonist protocol in poor responders undergoing IVF-ET

OBJECTIVE

To compare the efficacy and cost-effectiveness of extended high dose letrozole regimen/HPuFSH-gonadotropin releasing hormone antagonist (GnRHant) protocol with short low dose letrozole regimen/HPuFSH-GnRHant protocol in poor responders undergoing IVF-ET.

METHODS

In this randomized controlled trial, 136 women who responded poorly to GnRH agonist long protocol in their first IVF cycle were randomized into two equal groups using computer generated list and were treated in the second IVF cycle by either extended letrozole regimen (5 mg/day during the first 5 days of cycle and 2.5 mg/day during the subsequent 3 days) combined with HPuFSH-GnRHant protocol or short letrozole regimen (2.5 mg/day from cycle day 3-7) combined with HPuFSH-GnRHant protocol.

RESULTS

There were no significant differences between both groups with regard to number of oocytes retrieved and clinical pregnancy rate (5.39 ± 2.08 vs. 5.20 ± 1.88 and 22.06% vs. 16.18%, respectively).The total gonadotropins dose and medications cost per cycle were significantly lower in extended letrozole group (44.87 ± 9.16 vs. 59.97 ± 14.91 ampoules and 616.52 ± 94.97 vs. 746.84 ± 149.21 US Dollars ($), respectively).The cost-effectiveness ratio was 2794 $ in extended letrozole group and 4616 $ in short letrozole group.

CONCLUSION

Extended letrozole regimen/HPuFSH-GnRHant protocol was more cost-effective than short letrozole regimen/HPuFSH-GnRHant protocol in poor responders undergoing IVF-ET.

The use of high dose letrozole in ovulation induction and controlled ovarian hyperstimulation

Letrozole, an aromatase inhibitor, has been demonstrated to be effective as an ovulation induction and controlled ovarian hyperstimulation agent. However, dose administration has generally been limited to 5 days at 2.5 to 7.5 mg daily. We undertook a retrospective review of over 900 treatment cycles using letrozole in doses as high as 12.5 mg per day. Results indicate that such doses do indeed offer benefit to patients; in that there is increased follicular growth and a higher number of predicted ovulations with higher doses of the drug. However, increasing doses does not produce a detrimental effect upon endometrial thickness. High-dose letrozole may be of value in women who fail to respond adequately to lower doses. Furthermore, randomized trials are needed to determine whether high-dose letrozole might actually be optimal as a starting dose for certain treatment groups.

Extended letrozole regimen versus clomiphene citrate for superovulation in patients with unexplained infertility undergoing intrauterine insemination: a randomized controlled trial

BACKGROUND

The aim of this randomized controlled trial was to compare the efficacy of extended letrozole regimen with clomiphene citrate in women with unexplained infertility undergoing superovulation and intrauterine insemination (IUI).

METHODS

Two hundred and fourteen patients with unexplained infertility were randomized into two equal groups using computer generated list and were treated by either letrozole 2.5 mg/day from cycle day 1 to 9 (extended letrozole group, 211 cycles) or clomiphene citrate 100 mg/day from cycle day 3 to 7 (clomiphene citrate group,210 cycles). Intrauterine insemination was performed 36 to 40 hours after HCG administration.

RESULTS

Both groups were comparable with regard to number of mature follicles (2.24 +/- 0.80 Vs 2.13 +/- 0.76) and the day of HCG administration. Serum estradiol was significantly greater in clomiphene citrate group (356 +/- 151 Vs 822 +/- 302 pg/ml, P = < 0.001) and the endometrial thickness was significantly greater in extended letrozole group (9.10 +/- 1.84 Vs 8.18 +/- 1.93 mm, P = < 0.001).The pregnancy rate per cycle and cumulative pregnancy rate were significantly greater in extended letrozole group (18.96% Vs 11.43% and 37.73% Vs 22.86%, respectively).

CONCLUSION

The extended letrozole regimen had a superior efficacy as compared with clomiphene citrate in patients of unexplained infertility undergoing superovulation and IUI.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01232075.

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.

Extended letrozole therapy for ovulation induction in clomiphene-resistant women with polycystic ovary syndrome: a novel protocol

OBJECTIVE

To evaluate the outcome of long letrozole therapy for induction of ovulation in patients with clomiphene-resistant polycystic ovary syndrome (PCOS).

DESIGN

Prospective randomized controlled study.

SETTING

University teaching hospital and a private practice.

PATIENT(S)

The study comprised 218 patients with clomiphene-resistant PCOS.

INTERVENTION(S)

Patients were randomly allocated to treatment with either long letrozole therapy (n = 108; 219 cycles) or short letrozole therapy (n = 110; 225 cycles).

MAIN OUTCOME MEASURE(S)

Number of growing and mature follicles, serum E(2) (pg/mL), serum P (ng/mL), endometrial thickness, occurrence of pregnancy and miscarriage.

RESULT(S)

The number of ovulating patients was greater in the long letrozole group (65.7% vs. 61.8%), but without statistical differences. The total numbers of follicles during stimulation was significantly greater in the long letrozole group (6.7 +/- 0.3 vs. 3.9 +/- 0.4). The numbers of follicles > or =14 mm and > or =18 mm were significantly greater in the long letrozole group. There was no significant difference in the pretreatment endometrial thickness or endometrial thickness at the time of hCG administration between the two groups. Pregnancy occurred in 28 of 225 cycles in the short group (12.4%) and 38 of 219 cycles (17.4%) in the long letrozole group, and the difference was statistically significant.

CONCLUSION(S)

The long letrozole protocol (10 days) can produce more mature follicles and subsequently more pregnancies than the short letrozole therapy (5 days).

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.