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

Letrozole During Frozen Embryo Transfer in Women With Polycystic Ovarian Syndrome: A Randomized Controlled Trial

OBJECTIVE

To compare live-birth rates between letrozole application and artificial cycle for endometrium preparation during frozen embryo transfer (FET) cycle among women with polycystic ovarian syndrome (PCOS).

METHODS

A randomized controlled trial was conducted. Women with PCOS were randomized to letrozole application for ovulation induction compared with artificial cycle for endometrial preparation during FET. The primary outcome was live-birth rate per embryo transfer. Secondary outcomes included pregnancy-related outcomes, perinatal outcomes, and maternal complication rates. Assuming α=0.05 and 80% power, 186 patients per group were required to demonstrate a difference of 15% in live-birth rate: 205 patients (at least) per group were randomized to allow for a 10% dropout rate.

RESULTS

Four hundred twenty patients were enrolled from 2018 to 2021. Two hundred ten patients were assigned to the letrozole application group, and 210 were assigned to the artificial cycle group. There was no difference in the live-birth rate (42.4% vs 42.9%, P =>.99). There was no difference in secondary outcomes, including clinical pregnancy rate (51.4% vs 56.2%, P =.378), implantation rate (51.8% vs 55.8%, P =.401), and miscarriage rate (8.6% vs 11.0%, P =.511). For perinatal outcomes, singleton birth weight was significantly higher in the artificial cycle group (3,108±56 g vs 3,301±58, P =.018), and the incidence of gestational diabetes mellitus (GDM) was significantly higher in letrozole application group (14.6% vs 5.6%, P =.050). The other outcome was no difference in maternal complications.

CONCLUSION

There was no difference in pregnancy outcomes between letrozole application compared with artificial cycle for endometrial preparation in women with PCOS who underwent FET. The risk of GDM was higher in the letrozole application group, and the singleton birth weight was lower in the artificial cycle group.

CLINICAL TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR1800014746.

Letrozole vs clomiphene citrate in Sudanese patients with infertility secondary to polycystic ovary syndrome

PCOS is a cluster of metabolic, hormonal, and environmental factors coupled with infertility in patients within reproductive age. This cross-sectional study compared letrozole (LTZ) vs Clomiphene citrate (CC) as ovulation inducers in infertile Sudanese patients with PCOS. Follicles ≥18 mm and pregnancy tests were used for comparison. SPSS version 23 was used for analysis. Significance was calculated with Chi-square, t-test, and logistic regression. P ≤ 0.05 was considered significant.Our results showed 49% of the patients were 20-30 years old, 60% had secondary infertility 98.4% were secondary to PCOS and 64% had a family history of infertility. Comparable results on positive pregnancy tests of 26% (P ≤ 0.017) and 17% (P ≤ 0.027) were observed for LTZ vs CC respectively. Similar strengths (P ≤ 0.000) in compacting the ovarian cysts were recorded. LTZ showed less activity (P ≤ 0.013) on follicles size maturation compared to (P ≤ 0.000) with CC. The endometrial thickness was increased with LTZ (51.87%) but reduced with CC (25.54%). The positive pregnancy test was associated with age and BMI.

Conclusion

Letrozole 20 mg single dose showed comparable results on positive pregnancy tests but less significance on follicle maturation compared to CC100mg. Both drugs compacted the ovarian cysts' sizes. letrozole significantly increased the endometrial lining thickness.

Optimal lead follicle size in letrozole human menopausal gonadotrophin intrauterine insemination cycles with and without spontaneous LH surge

RESEARCH QUESTION

What is the optimal lead follicle size in letrozole, human menopausal gonadotrophin and intrauterine insemination (IUI) cycles with and without spontaneous LH surges?

DESIGN

This retrospective cohort study included 3797 letrozole HMG IUI cycles between January 2010 and May 2021. All cycles were divided into two groups: the HCG trigger group (trigger day LH ≤15 mIU/ml) and the spontaneous LH surge group (trigger day LH >15 mIU/ml). These two groups were subdivided into smaller groups based on the diameter of the follicles. The primary outcome measure was clinical pregnancy rate. Logistic regression analysis was conducted to explore other risk factors.

RESULTS

In the HCG trigger group, the clinical pregnancy rate varied significantly, with rates of 20.8%, 14.9% and 11.8% for the 16.1-18.0, 18.1-20.0 and 20.1-22.0 mm groups, respectively (P = 0.005). In the spontaneous LH surge group, the pregnancy rate of follicles within 14.1-16.0 mm was significantly higher than that of follicles within 20.1-22.0 mm (adjusted OR 0.533, 95% CI 0.308 to 0.923, P = 0.025). Also, patients with two lead follicles were 2.569 times more likely to achieve a clinical pregnancy than those with only one lead follicle (adjusted OR 2.569, 95% CI 1.258 to 5.246, P = 0.010). The duration of infertility was also found to be a common influencing factor in both groups.

CONCLUSIONS

The optimal lead follicle size was between 16.1 and 18.0 mm in HCG-triggered letrozole HMG IUI cycles. If the lead follicle size is relatively small (14.1-18.0 mm) when a spontaneous LH surge occurs, there is no need to cancel the IUI cycle.

DUAL TRIGGER STRATEGY AFTER CONTROLLED STIMULATION INTRAUTERINE INSEMINATION CYCLE DID NOT INFLUENCE THE PREGNANCY OUTCOME COMPARED WITH STANDARD HCG TRIGGER ONLY PROTOCOL

OBJECTIVE

The aim: A prospective randomized comparative study was conducted to investigate the effect of dual trigger, using gonadotropin releasing hormone agonist with human chorionic gonadotropin (hCG) versus hCG alone, for ovulation trigger in controlled ovarian stimulation intrauterine insemination (IUI) cycle on pregnancy outcome.

PATIENTS AND METHODS

Materials and methods: Ninety women were randomly allocated into equal groups to trigger ovulation for IUI cycle using either method; IUI was performed following 36-42 hours post triggering. Luteinizing hormone (LH) and progesterone levels were measured at insemination day.

RESULTS

Results: The baseline of demographic and clinical characteristics of both groups was similar. Progesterone level was higher in dual trigger group than in hCG alone group (1.61 versus 0.71 ng/mL, P≤0.0001); while LH level was lower in dual trigger group (19.35 versus 24.51 IU/L, P≤0.014). Furthermore, LH level at the day of IUI was higher in pregnant women than in non-pregnant (27.9 versus 20 IU/L, P≤0.007).

CONCLUSION

Conclusions: Pregnancy rate was equivalent in both groups. More intensive investigation is required to study the efficacy of the dual trigger in IUI cycle.

The Effect of Spontaneous LH Surges on Pregnancy Outcomes in Patients Undergoing Letrozole-HMG IUI: A Retrospective Analysis of 6,285 Cycles

BACKGROUND

To date, no consensus has been reached on whether to wait for spontaneous luteinizing hormone (LH) surge to occur or to trigger ovulation regardless of the presence of an LH surge for achieving higher success rate in intrauterine insemination (IUI) cycles. Therefore, we hope to investigate the effect of the presence of a spontaneous LH surge on pregnancy outcomes in letrozole-human menopausal gonadotropin (LE-HMG) IUI cycles.

METHODS

In this retrospective cohort study, a total of 6,285 LE-HMG IUI cycles were included between January 2010 and May 2021. Cycles were categorized into three groups: the trigger + LH surge group, the trigger only group, and the LH surge only group. The primary outcome measure was the clinical pregnancy rate. A logistic regression analysis was performed to explore other risk factors affecting the clinical pregnancy rate.

RESULTS

No significant differences were observed in biochemical pregnancy rate (P =0.640), clinical pregnancy rate (P =0.702), ongoing pregnancy rate (P =0.842), and live birth rate (P =0.951) among the three groups. The binary logistic regression analysis also confirmed that the existence of an LH surge was not associated with clinical pregnancy. There was a difference in ectopic pregnancy rates (P =0.045), but logistic regression showed that the presence of a spontaneous LH surge has no association with ectopic pregnancy. Nonetheless, patients with lead follicles within 18.1-20.0 mm/20.1-22.0 mm and a long duration of LE treatment were less likely to get ectopic pregnant compared with patients with 14.1-16.0 mm lead follicles and shorter LE treatment (OR: 0.142, 95% CI: 0.023-0.891, P =0.037; OR: 0.142, 95% CI: 0.022-0.903, P =0.039; OR: 0.445, 95% CI: 0.235-0.840, P = 0.013).

CONCLUSIONS

The presence of a spontaneous LH surge in triggered LE-HMG IUI cycles does not appear to improve pregnancy rates. Thus, we suggest that waiting for an LH surge to occur is not necessary in triggered LE-HMG IUI cycles.

Controlled ovarian stimulation should not be preferred for male infertility treated with intrauterine insemination: a retrospective study

BACKGROUND

Some studies have stated that intrauterine insemination (IUI) with controlled ovarian stimulation (COS) might increase the pregnancy rate, while others suggest that IUI in the natural cycle (NC) should be the first line of treatment. It remains unclear whether it is necessary to use COS at the same time when IUI is applied to treat isolated male factor infertility. Thus, we aimed to investigate efficacy of IUI with COS for isolated male factor infertility.

METHODS

A total of 601 IUI cycles from 307 couples who sought medical care for isolated male factor infertility between January 2010 and February 2020 were divided into two groups: NC-IUI and COS-IUI. The COS-IUI group was further divided into two subgroups according to the number of pre-ovulatory follicles on the day of HCG: cycles with monofollicular development (one follicle group) and cycles with at least two pre-ovulatory follicles (≥ 2 follicles group). The IUI outcomes, including clinical pregnancy, live birth, spontaneous abortion, ectopic pregnancy, and multiple pregnancy rates were compared.

RESULTS

The clinical pregnancy, live birth, spontaneous abortion, and ectopic pregnancy rates were comparable between the NC-IUI and COS-IUI group. Similar results were also observed among the NC-IUI, one follicle, and ≥ 2 follicles groups. However, with respect to the multiple pregnancy rate, a trend toward higher multiple pregnancy rate was observed in the COS-IUI group compared to the NC-IUI group (8.7% vs. 0, P = 0.091), and a significant difference was found between the NC-IUI and ≥ 2 follicles group (0 vs. 16.7%, P = 0.033).

CONCLUSION

In COS cycles, especially in those with at least two pre-ovulatory follicles, the multiple pregnancy rate increased without a substantial gain in overall pregnancy rate; thus, COS should not be preferred in IUI for isolated male factor infertility. If COS is required, one stimulated follicle and one healthy baby should be the goal considering the safety of both mothers and foetuses.

Therapeutic Potentials of Low-Dose Tacrolimus for Aberrant Endometrial Features in Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a major anovulatory infertility affecting a great proportion of women of childbearing age and is associated with obesity, insulin resistance and chronic inflammation. Poor endometrial receptivity and recurrent implantation failure are major hurdles to the establishment of pregnancy in women with PCOS. The accumulating body of evidence obtained from experimental and clinical studies suggests a link between inherent adaptive and innate immune irregularities and aberrant endometrial features in PCOS. The use of conventional therapeutic interventions such as lifestyle modification, metformin and ovarian stimulation has achieved limited clinical success in restoring ovulation and endometrial receptivity in women with PCOS. Unlike other immunosuppressive drugs prescribed in the clinical management of autoimmune and inflammatory disorders that may have deleterious effects on fertility and fetal development, preclinical studies in mice and in women without PCOS but with repeated implantation failure revealed potential therapeutic benefits for the use of low-dose tacrolimus in treating female infertility. Improved systemic and ovarian immune functions, endometrial progesterone receptor and coreceptor expressions and uterine vascular adaptation to pregnancy were among features of enhanced progesterone-receptor sensitivity in the low-dose tacrolimus-treated mouse model of the disease. In this review, we have compiled available experimental and clinical data in literature on endometrial progesterone resistance and current therapeutic options, as well as mechanisms of actions and reported outcomes relevant to the potential therapeutic benefits for the use of low-dose tacrolimus in treating PCOS-associated female infertility.

The impact of ovarian stimulation on the outcome of intrauterine insemination treatment: an analysis of 8893 cycles

OBJECTIVE

To evaluate the impact of ovarian stimulation on the outcome of intrauterine insemination (IUI).

DESIGN

Retrospective analysis.

SETTING

A single university-based centre.

POPULATION

A total of 5109 couples with 8893 cycles.

METHODS

The outcome of IUI with different protocols for ovarian stimulation was examined.

MAIN OUTCOME MEASURES

The live birth rate (LBR), twin pregnancy rate and ovarian hyperstimulation syndrome (OHSS).

RESULTS

In ovulatory women without ovarian stimulation, the LBR was 7.6%. Stimulation with clomifene citrate (CC), letrozole (LE), human menopausal gonadotrophin (HMG), CC or LE combined with HMG achieved LBRs of 6.1, 5, 7.9, 8 and 12.2%, respectively. LE combined with HMG achieved a significantly improved LBR compared with no stimulation. HMG stimulation was associated with a higher rate of twins (7.4%) than no stimulation (0%, P < 0.01). In ovulatory women, the LBR appeared lower in CC and LE compared with no stimulation (P > 0.05). In anovulatory women, ovarian stimulation with CC, LE, HMG, CC or LE combined with HMG achieved LBRs of 11.3, 5.1, 11.8, 12.6 and 13.6%, respectively. No significant difference was observed. There were no triplet pregnancies or OHSS in stimulated cycles.

CONCLUSIONS

In ovulatory women, ovarian stimulation with LE combined with HMG achieved a significantly improved live birth rate. HMG stimulation resulted in a high risk for twins.

TWEETABLE ABSTRACT

In ovulatory women, ovarian stimulation with letrozole and HMG resulted in a significantly improved LBR.

The curious case of premature luteinization

PURPOSE

Premature luteinization (PL) affects 12.3-46.7% of fresh in vitro fertilization cycles, and there is accumulating evidence confirming its negative effect on success rates. However, despite its clinical significance, PL is poorly understood and defined. This narrative review aims to provide a fresh look at the phenomenon of PL by summarizing the existing evidence and re-evaluating fundamental issues.

METHODS

A thorough electronic search was conducted covering the period from 1978 until January 2018 in PubMed, Embase, and Medline databases, and references of relevant studies were cross-checked. Meeting proceedings of the European Society of Human Reproduction and Embryology and the American Society for Reproductive Medicine were also hand searched.

RESULTS

In the curious case of PL, one should go back to the beginning and re-consider every step of the way. The pathogenesis, definition, measurement methods, clinical implications, and management strategies are discussed in detail, highlighting controversies and offering "food for thought" for future directions.

CONCLUSIONS

Authors need to speak the same language when studying PL in order to facilitate comparisons. The terminology, progesterone cut-off, measurement methods and days of measurement should be standardized and globally accepted; otherwise, there can be no scientific dialog. Future research should focus on specific patient profiles that may require a tailored approach. Progesterone measurements throughout the follicular phase possibly depict the progesterone exposure better than an isolated measurement on the day of hCG. Adequately powered randomized controlled trials should confirm which the best prevention and management plan of PL is, before introducing any strategy into clinical practice.

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 .

Reversal of tubo-ovarian atypical epithelial patterns after cessation of ovarian stimulation by letrozole

Letrozole (LTZ), one of the ovulation induction medications, is increasingly prescribed in various gynaecological conditions. Previous studies have demonstrated its potential hazardous effect on the ovarian surface epithelium (OSE) as well as on tubal epithelial cells (TEC). However, it is not clear whether this effect could be reversed by LTZ cessation. Therefore, the objective of our study was to investigate the effect of stoppage of LTZ on these cells after 12 cycles of ovarian stimulation. A total of 54 Sprague Dawley rats were used in this study, divided equally into control, LTZ12 and CES12 groups (received saline, 12 cycles of LTZ and 12 cycles of cessation post-LTZ12 respectively). Samples from the ovaries as well as fallopian tubes (FTs) were studied histologically for the changes associated with LTZ12 and CES12 respectively. There was evident increase in the proliferative activity and Ki67 immunoexpression in the OSE of LTZ12. The OSE was hyperchromatic, and abnormally frequent deep invaginations, micropapillae and cortical cysts. Their TEC showed frequent multilayering, papillary projections and loss of cilia. Almost all these changes disappeared 12 cycles after LTZ cessation. While the tubal IL-1β, IL-6, TNF-α and serum MCP-1 levels significantly increased in the LTZ12 group compared with the control group, their levels decreased in the CES12 group compared with those of the control. Therefore, the abnormal tubo-ovarian epithelial patterns may completely regress after cessation of LTZ stimulation for a reasonable duration. This is a potentially good omen and a positive indicator of the relatively safe use of LTZ after its intake has been stopped.

Comparison of the Effect of Clomiphene- Estradiol Valerate vs Letrozole on Endometrial Thickness, Abortion and Pregnancy Rate in Infertile Women with Polycystic Ovarian Syndrome

INTRODUCTION

Clomiphene citrate is the first-line therapy for ovulation induction in Polycystic Ovarian Syndrome (PCOS). This drug binds and blocks estrogen receptors and thought to have an anti estrogenic effect on endometrium volume, thus may have adverse effect on fertility.

AIM

This study aimed to compare the effect of Clomiphene citrate plus Estradiol Valerate with Letrozole on endometrial thickness, abortion and pregnancy rate in infertile women with PCOS undergoing ovulation induction.

MATERIALS AND METHODS

This was a randomized double blind clinical trial study on 100 women with PCOS, with an endometrial thickness less than 7mm in spite of follicles greater than 18mm after administration of Clomiphene citrate 100mg/d from 3(th) to 7(th) day of menstruation. They were randomly divided in two groups. Group A received 100mg Clomiphene citrate from day 3 to day 7 of menstruation and 4 mg Estradiol Valerate after the 8(th) day of menstruation until 14(th) day. Group B treated by 5mg Letrozole from day 3 to 7 of menstruation with placebo from 8(th) to 14(th) day of menstruation. In both groups endometrial thickness was measured by transvaginal sonography in the 14(th) day of menstruation. Data were analysed using SPSS Ver.18.0.

RESULTS

The mean age was 30.34 years in group A and 29.62 years in group B (p=0.381). The number of infertility years in group A was 3.73 years and in group B was 3.85 years. There was no significant relationship statistically between the two groups in terms of mean age and infertility years (p=0.99). Endometrial thickness in group A was 7.26mm and in group B was 8.17 mm. Pregnancy rates in group A and group B was 32% and 16% respectively. There was significant relationship statistically between the two groups in terms of endometrial thickness and pregnancy rates (p=0.021 and p=0.05). There was no abortion in group A and 5 cases had abortion in group B, there was a significant relationship between the two groups statistically (p=0.028).

CONCLUSION

Letrozole increased endometrial thickness and pregnancy rate in infertile women, therefore its administration is recommended.

Controlled ovarian hyperstimulation with sequential letrozole co-treatment in normo/high responders

OBJECTIVE

To investigate the effect of co-administration of letrozole in an ovarian stimulation protocol using recombinant FSH and GnRH antagonists for ICSI in normo/high responders.

METHODS

Computerized data of 320 antagonist ICSI/ET cycles with or without letrozole were retrospectively analyzed. In 105 cases, letrozole (5 mg/day) was started at the second day of the cycle continued for 5 days. At the second day of letrozole, gonadotropins were added. The remaining 215 cases were stimulated with recombinant FSH only. In all cases on day 6, GnRH antagonist was started. Ovarian stimulation protocols with or without letrozole were compared for cycle outcome parameters.

RESULTS

In cycles with letrozole, significantly lower gonadotropin consumption and lower peak estradiol levels were found. In cycles with letrozole, mean number of metaphase II and fertilized oocytes retrieved were significantly higher compared to cycles without letrozole. The pregnancy and clinical pregnancy rates were similar.

CONCLUSION

Should the number of oocytes retrieved being higher in letrozole group might indicate that letrozole might contribute to successful ovarian stimulation with a lower dosage of gonadotropins. Despite the lower peak estradiol levels, pregnancy rates being similar to other group also support the idea that letrozole can contribute to normal potential of implantation.

A Randomized Clinical Trial on Comparing The Cycle Characteristics of Two Different Initiation Days of Letrozole Treatment in Clomiphene Citrate Resistant PCOS Patients in IUI Cycles

Background

There are still many questions about the ideal protocol for letrozole (LTZ) as the commonest aromatase inhibitor (AI) used in ovulation induction. The aim of this study is to compare the ultrasonographic and hormonal characteristics of two different initiation times of LTZ in clomiphene citrate (CC) failure patients and to study androgen dynamics during the cycle.

Materials and Methods

This randomized clinical trial was done from March to November 2010 at the Mashhad IVF Center, a university based IVF center. Seventy infertile polycystic ovarian syndrome (PCOS) patients who were refractory to at least 3 CC treatment cycles were randomly divided into two groups. Group A (n=35) receiving 5 mg LTZ on cycle days 3-7 (CD3), and group B (n=35) receiving the same amount on cycle days 5-9 (CD5). Hormonal profile and ultrasonographic scanning were done on cycle day 3 and three days after completion of LTZ treatment (cycle day 10 or 12). Afterward, 5,000-10,000 IU human chorionic gonadotropin (hCG) was injected if at least one follicle ≥18 mm was seen in ultrasonographic scanning. Intrauterine insemination (IUI) has been done 36-40 hours later. The cycle characteristics, the ovulation and pregnancy rate were compared between two groups. The statistical analysis was done using Fisher’s exact test, t test, logistic regression, and Mann-Whitney U test.

Results

There were no significant differences between two groups considering patient characteristics. The ovulation rate (48.6 vs. 32.4% in group A and B, respectively), the endometrial thickness, the number of mature follicles, and length of follicular phase were not significantly different between the two groups.

Conclusion

LTZ is an effective treatment in CC failure PCOS patients. There are no significant differences regarding ovulation and pregnancy rates between two different protocols of LTZ starting on days 3 and 5 of menstrual cycle (Registration Number: IRCT201307096467N3).

Effect of vehicle and route of administration of letrozole on ovarian function in a bovine model

The objective of this study was to determine the effects of vehicle and route of administration of letrozole on ovarian function in sexually mature beef heifers. On Day 3 (Day 0 = ovulation), heifers were assigned randomly to four treatment groups and given 1 mg kg–1 letrozole intravenously (iv, n = 10) or intramuscularly (im, n = 10) or given a placebo iv (control iv, n = 5) or im (control im, n = 5). The interwave interval was longer in heifers treated with letrozole im than in im and iv controls (11.7 ± 0.30 vs 9.5 ± 0.50 and 10 ± 0.43, respectively; P < 0.05). Corpus luteum diameter profiles and plasma progesterone concentrations were greater (P < 0.03 and P < 0.05, respectively) in heifers treated with letrozole im compared with control im. Plasma oestradiol concentrations were lower in both letrozole-treated groups compared with controls (P ≤ 0.03). Plasma LH concentrations tended to be elevated at the time of wave emergence in heifers treated with letrozole im compared with other groups (group-by-day interaction, P = 0.06) and plasma FSH concentrations tended to be greater (P < 0.09) in heifers treated with letrozole by either route compared with a single control group. We conclude that intramuscular administration of letrozole in oil is a feasible route and vehicle for the development of a letrozole-based treatment protocol for herd synchronisation in cattle.

Letrozole ovulation induction: an effective option in endometrial preparation for frozen-thawed embryo transfer

PURPOSE

To evaluate the clinical efficacy of letrozole on ovulation induction and hormone replacement therapy (HRT) during endometrial preparation for frozen-thawed embryo transfer (FET).

METHODS

We analyzed totally 1,230 cycles of patients that underwent FET from October 2010 to September 2012. Seven hundred and thirteen cycles of patients with ovulation disorders that underwent FET were randomly assigned to two groups by case control study. 359 cycles received letrozole ovulation induction and 354 cycles received HRT during endometrial preparation for FET, respectively. In the corresponding period, 517 cycles of patients with normal ovulation in the natural cycle group for FET endometrial preparation served as controls. Reproduction-related clinical outcomes of patients in the three groups were compared.

RESULTS

The embryo implantation rate of patients in letrozole group (30.4 %) was significantly higher than the HRT group (22.8 %, P < 0.05). The clinical pregnancy rate of patients in the letrozole group (53.2 %) was significantly higher than the HRT group (44.4 %, P < 0.05), while no significant difference was observed between the letrozole and natural cycle groups (51.3 %, P > 0.05). Estradiol levels on the day of human chorionic gonadotropin administration in the letrozole group were significantly lower than those in the natural cycle group (280.32 ± 125.39 pg/ml and 351.06 ± 123.03 pg/ml, respectively; P < 0.05). The live birth rate of patients in letrozole group (44.6 %) was significantly higher than the HRT group (32.5 %, P < 0.05), while abortion rate (12.0 %) was significantly lower than the HRT group (21.0 %, P < 0.05). There were no significant differences in number of mature follicles, endometrial thickness, duration of follicle growth between the letrozole and the natural cycle groups, and there were no significant differences in twin birth rate and ectopic pregnancy rate among the three groups (all P values >0.05).

CONCLUSIONS

Ovulation induction with letrozole during endometrial preparation for FET has a higher rate of pregnancy success and a lower abortion rate than HRT. Letrozole treatment exhibits clinical progression and outcomes similar to those patients undergoing a natural cycle or normal ovulation cycle. Therefore, letrozole treatment may be an effective option in endometrial preparation for FET in patients with ovulation disorders or irregular menstruation.

The aromatase inhibitor letrozole reduces adhesion formation after intraperitoneal surgery in a rat uterine horn model

OBJECTIVE

To investigate, in an experimental animal study, the effects of letrozole and tamoxifen in the reduction of adhesion formation following abdominopelvic surgery.

STUDY DESIGN

Thirty female Wistar albino rats were included and divided into three groups. One group received 500 μg/d tamoxifen and a second group received 1 mg/kg/d letrozole through an enteric tube. A third group did not receive any drugs and served as the control group. On the fifth day, a laparotomy was performed and the right uterine horn was injured by monopolar cautery. The left uterine horn was incised with a scalpel and sutured. The preventive therapy protocols were continued for 7 days after surgery. On the 14th day after first surgery the animals were sacrificed, and the intraperitoneal macroscopic adhesion formation and microscopic adhesion features were evaluated. The Kruskal-Wallis test was used to compare the scores of the macroscopic adhesion scores and histologic features among the three groups, followed by a post hoc Mann-Whitney test. The total histological score was analyzed with a one-way ANOVA, followed by post hoc Bonferroni correction tests. p values ≤0.05 were considered statistically significant. The level of significance was set at p≤0.016 for the post hoc tests.

RESULTS

The letrozole and tamoxifen groups had significantly lower adhesion scores for the right uterine horn than the control group (p=0.005 and p=0.013, respectively). For the left horn, however, only the letrozole group had a lower macroscopic adhesion score than the controls (p=0.011). The total histological score was significantly lower in the letrozole group than in the control group (p=0.014), but no differences were found between the tamoxifen group and the control group (p=0.954). Inflammation, fibroblastic activity, collagen formation and vascular proliferation were significantly lower in the letrozole group compared with the control group (p<0.05). The foreign body reactions were similar among the three groups (p>0.05). Tamoxifen administration did not result in any significant effects on the histological scores (p>0.05).

CONCLUSION

Letrozole resulted in a significant decrease in postoperative macroscopic adhesion formation and the total histological scores, but tamoxifen did not demonstrate a similar effect on the histological scores.