Bi-allelic variants in DNAH10 cause asthenoteratozoospermia and male infertility

Further evidence from DNAH12 supports favorable fertility outcomes of infertile males with dynein axonemal heavy chain gene family variants

Male infertility is a major concern affecting reproductive health. Biallelic deleterious variants of most DNAH gene family members have been linked to male infertility, with intracytoplasmic sperm injection (ICSI) being an efficacious way to achieve offspring. However, the association between DNAH12 and male infertility is still limited. Here, we identified one homozygous variant and two compound heterozygous variants in DNAH12 from three infertile Chinese men. Semen analysis revealed severe asthenozoospermia, abnormal morphology, and structure of sperm flagella. Furthermore, the Dnah12 knock-out mouse revealed severe spermatogenesis failure and validated the same male infertility phenotype. Favorable fertility outcomes were achieved through ICSI in three human individuals and Dnah12 knock-out mice. Collectively, our study indicated that biallelic variants of DNAH12 can induce male infertility in both human beings and mice. Notably, evidence from DNAH12 enhanced that ICSI was an optimal intervention to achieve favorable fertility outcomes for infertile males with DNAH gene family variants.

Bi-allelic variants in DNAH3 cause male infertility with asthenoteratozoospermia in humans and mice

STUDY QUESTION

Are there other pathogenic genes for asthenoteratozoospermia (AT)?

SUMMARY ANSWER

DNAH3 is a novel candidate gene for AT in humans and mice.

WHAT IS KNOWN ALREADY

AT is a major cause of male infertility. Several genes underlying AT have been reported; however, the genetic aetiology remains unknown in a majority of affected men.

STUDY DESIGN SIZE DURATION

A total of 432 patients with AT were recruited in this study. DNAH3 mutations were identified by whole-exome sequencing (WES). Dnah3 knockout mice were generated using the genome editing tool. The morphology and motility of sperm from Dnah3 knockout mice were investigated. The entire study was conducted over 3 years.

PARTICIPANTS/MATERIALS SETTING METHODS

WES was performed on 432 infertile patients with AT. In addition, two lines of Dnah3 knockout mice were generated. Haematoxylin and eosin (H&E) staining, transmission electron microscopy (TEM), immunostaining, and computer-aided sperm analysis (CASA) were performed to investigate the morphology and motility of the spermatozoa. ICSI was used to overcome the infertility of one patient and of the Dnah3 knockout mice.

MAIN RESULTS AND THE ROLE OF CHANCE

DNAH3 biallelic variants were identified in three patients from three unrelated families. H&E staining revealed various morphological abnormalities in the flagella of sperm from the patients, and TEM and immunostaining further showed the loss of the central pair of microtubules, a dislocated mitochondrial sheath and fibrous sheath, as well as a partial absence of the inner dynein arms. In addition, the two Dnah3 knockout mouse lines demonstrated AT. One patient and the Dnah3 knockout mice showed good treatment outcomes after ICSI.

LARGE SCALE DATA

N/A.

LIMITATIONS REASONS FOR CAUTION

This is a preliminary report suggesting that defects in DNAH3 can lead to asthenoteratozoospermia in humans and mice. The pathogenic mechanism needs to be further examined in a future study.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings show that DNAH3 is a novel candidate gene for AT in humans and mice and provide crucial insights into the biological underpinnings of this disorder. The findings may also be beneficial for counselling affected individuals.

STUDY FUNDING/COMPETING INTERESTS

This work was supported by grants from National Natural Science Foundation of China (82201773, 82101961, 82171608, 32322017, 82071697, and 81971447), National Key Research and Development Program of China (2022YFC2702604), Scientific Research Foundation of the Health Committee of Hunan Province (B202301039323, B202301039518), Hunan Provincial Natural Science Foundation (2023JJ30716), the Medical Innovation Project of Fujian Province (2020-CXB-051), the Science and Technology Project of Fujian Province (2023D017), China Postdoctoral Science Foundation (2022M711119), and Guilin technology project for people's benefit (20180106-4-7). The authors declare no competing interests.

Novel variants in DNAH6 cause male infertility associated with multiple morphological abnormalities of the sperm flagella (MMAF) and ICSI outcomes

Variations in the dynein axonemal heavy chain gene, dynein axonemal heavy chain 6 ( DNAH6 ), lead to multiple morphological abnormalities of the flagella. Recent studies have reported that these deficiencies may result in sperm head deformation. However, whether DNAH6 is also involved in human acrosome biogenesis remains unknown. The purpose of this study was to investigate DNAH6 gene variants and their potential functions in the formation of defective sperm heads and flagella. Whole-exome sequencing was performed on a cohort of 375 patients with asthenoteratozoospermia from the First Affiliated Hospital of Anhui Medical University (Hefei, China). Hematoxylin and eosin staining, scanning electron microscopy, and transmission electron microscopy were performed to analyze the sperm morphology and ultrastructure. Immunofluorescence staining and Western blot analysis were conducted to examine the effects of genetic variants. We identified three novel deleterious variants in DNAH6 among three unrelated families. The absence of inner dynein arms and radial spokes was observed in the sperm of patients with DNAH6 variants. Additionally, deficiencies in the acrosome, abnormal chromatin compaction, and vacuole-containing sperm heads were observed in these patients with DNAH6 variants. The decreased levels of the component proteins in these defective structures were further confirmed in sperm from patients with DNAH6 variants using Western blot. After intracytoplasmic sperm injection (ICSI) treatment, the partner of one patient with a DNAH6 variant achieved successful pregnancy. Overall, novel variants in DNAH6 genes that contribute to defects in the sperm head and flagella were identified, and the findings indicated ICSI as an effective clinical treatment for such patients.

Dynein axonemal heavy chain 10 deficiency causes primary ciliary dyskinesia in humans and mice

Primary ciliary dyskinesia (PCD) is a congenital, motile ciliopathy with pleiotropic symptoms. Although nearly 50 causative genes have been identified, they only account for approximately 70% of definitive PCD cases. Dynein axonemal heavy chain 10 (DNAH10) encodes a subunit of the inner arm dynein heavy chain in motile cilia and sperm flagella. Based on the common axoneme structure of motile cilia and sperm flagella, DNAH10 variants are likely to cause PCD. Using exome sequencing, we identified a novel DNAH10 homozygous variant (c.589C > T, p.R197W) in a patient with PCD from a consanguineous family. The patient manifested sinusitis, bronchiectasis, situs inversus, and asthenoteratozoospermia. Immunostaining analysis showed the absence of DNAH10 and DNALI1 in the respiratory cilia, and transmission electron microscopy revealed strikingly disordered axoneme 9+2 architecture and inner dynein arm defects in the respiratory cilia and sperm flagella. Subsequently, animal models of Dnah10-knockin mice harboring missense variants and Dnah10-knockout mice recapitulated the phenotypes of PCD, including chronic respiratory infection, male infertility, and hydrocephalus. To the best of our knowledge, this study is the first to report DNAH10 deficiency related to PCD in human and mouse models, which suggests that DNAH10 recessive mutation is causative of PCD.

DNALI1 deficiency causes male infertility with severe asthenozoospermia in humans and mice by disrupting the assembly of the flagellar inner dynein arms and fibrous sheath

The axonemal dynein arms (outer (ODA) and inner dynein arms (IDAs)) are multiprotein structures organized by light, intermediate, light intermediate (LIC), and heavy chain proteins. They hydrolyze ATP to promote ciliary and flagellar movement. Till now, a variety of dynein protein deficiencies have been linked with asthenospermia (ASZ), highlighting the significance of these structures in human sperm motility. Herein, we detected bi-allelic DNALI1 mutations [c.663_666del (p.Glu221fs)], in an ASZ patient, which resulted in the complete loss of the DNALI1 in the patient's sperm. We identified loss of sperm DNAH1 and DNAH7 rather than DNAH10 in both DNALI1^663_666del patient and Dnali1^-/- mice, demonstrating that mammalian DNALI1 is a LIC protein of a partial IDA subspecies. More importantly, we revealed that DNALI1 loss contributed to asymmetries in the most fibrous sheath (FS) of the sperm flagellum in both species. Immunoprecipitation revealed that DNALI1 might interact with the cytoplasmic dynein complex proteins in the testes. Furthermore, DNALI1 loss severely disrupted the transport and assembly of the FS proteins, especially AKAP3 and AKAP4, during flagellogenesis. Hence, DNALI1 may possess a non-classical molecular function, whereby it regulates the cytoplasmic dynein complex that assembles the flagella. We conclude that a DNALI deficiency-induced IDAs injury and an asymmetric FS-driven tail rigid structure alteration may simultaneously cause flagellum immotility. Finally, intracytoplasmic sperm injection (ICSI) can effectively resolve patient infertility. Collectively, we demonstrate that DNALI1 is a newly causative gene for AZS in both humans and mice, which possesses multiple crucial roles in modulating flagellar assembly and motility.

Novel HYDIN variants associated with male infertility in two Chinese families

INTRODUCTION

Infertility is a major disease affecting human life and health, among which male factors account for about half. Asthenoteratozoospermia accounts for the majority of male infertility. High-throughput sequencing techniques have identified numerous variants in genes responsible for asthenoteratozoospermia; however, its etiology still needs to be studied.

METHOD

In this study, we performed whole-exome sequencing on samples from 375 patients with asthenoteratozoospermia and identified two HYDIN compound heterozygous variants, a primary ciliary dyskinesia (PCD)-associated gene, in two unrelated subjects. H&E staining, SEM were employed to analyze the varies on sperm of patients, further, TEM was employed to determine the ultrastructure defects. And westernblot and immunostaining were chose to evaluate the variation of structural protein. ICSI was applied to assist the mutational patient to achieve offspring.

RESULT

We identified two HYDIN compound heterozygous variants. Patient AY078 had novel compound heterozygous splice variants (c.5969-2A>G, c.6316+1G>A), altering the consensus splice acceptor site of HYDIN. He was diagnosed with male infertility and PCD, presenting with decreased sperm progressive motility and morphological abnormalities, and bronchial dilatation in the inferior lobe. Compared to the fertile control, HYDIN levels, acrosome and centrosome markers (ACTL7A, ACROSIN, PLCζ1, and Centrin1), and flagella components (TOMM20, SEPT4, SPEF2, SPAG6, and RSPHs) were significantly reduced in HYDIN-deficient patients. Using intracytoplasmic sperm injection (ICSI), the patient successfully achieved clinical pregnancy. AY079 had deleterious compound heterozygous missense variants, c.9507C>G (p. Asn3169Lys) and c.14081G>A (p. Arg4694His), presenting with infertility; however, semen samples and PCD examination were unavailable.

DISCUSSION

Our findings provide the first evidence that the loss of HYDIN function causes asthenoteratozoospermia presenting with various defects in the flagella structure and the disassembly of the acrosome and neck. Additionally, ICSI could rescue this failure of insemination caused by immobile and malformed sperm induced by HYDIN deficiency.

Novel FSIP2 Variants Induce Super-Length Mitochondrial Sheath and Asthenoteratozoospermia in Humans

Asthenoteratozoospermia is one of the major factors for male infertility, whereas the causes of large numbers of cases are still unknown. We identified compound heterozygous variants of FSIP2 in three unrelated individuals from a cohort of 105 patients with asthenoteratozoospermia by exome sequencing. Deleterious FSIP2 variations caused severe disassembly of the fibrous sheath and axonemal defects. Intriguingly, spermatozoa in our study manifested "super-length" mitochondrial sheaths, increased levels of the mitochondrial sheath outer membrane protein TOMM20 and decreased mitochondrial ATP consumption. Dislocation or deletion of the annulus and reduction or dislocation of the annulus protein SEPT4 were also observed. While the lengthened mitochondrial sheaths were not presented in men harboring SEPT4 variants. Furthermore, female partners of two of three men achieved successful pregnancies following intracytoplasmic sperm injection (ICSI). Overall, we presume that FSIP2 may not only serve as a structural protein of the fibrous sheath but also as an intra-flagellar transporter involving in the axonemal assembly, mitochondrial selection and the termination of mitochondrial sheath extension during spermatogenesis, and ICSI is an effective treatment for individuals with FSIP2-associated asthenoteratozoospermia.

WDR87 interacts with CFAP47 protein in the middle piece of spermatozoa flagella to participate in sperm tail assembly

Spermatogenesis is a complex process that includes spermatogonia self-renewal, spermatocyte meiosis and spermatozoa assembly. Recent studies have revealed that WD40-repeat domain-containing (WDR) proteins play important roles in spermatocyte division, spermatozoa flagella assembly and head shaping. In this study, we investigated the expression pattern of WDR87 and found that it was highly expressed in the testis of both humans and mice. Immunofluorescence staining revealed that mouse WDR87 was distributed in the perinuclear cytoplasm of primary spermatocytes, secondary spermatocytes and round spermatids. In the spermiogenesis stage, with extension of the nucleus, WDR87 migrated to the manchette and finally localized to the middle piece of the spermatozoa tail. Furthermore, we identified a cilia- and flagella-associated protein, CFAP47, which interacted with WDR87 in the flagellar midpiece of the spermatozoa, suggesting that WDR87 may be associated with multiple morphological abnormalities of the flagella (MMAF). Subsequently, we screened gene mutations in seven MMAF individuals and found two novel mutations in CFAP47 (c.706G>A, Val236Met; c.1337C>T, Thr446Met) in one case. Immunoblotting and immunofluorescence revealed that CFAP47 was dramatically reduced in spermatozoa from the CFAP47-mutated man. Meanwhile, the expression of WDR87 was also significantly decreased, and weak signals were detected adjacent to the spermatozoa nuclei, indicating that CFAP47 was necessary for WDR87 transportation during spermatozoa flagella biogenesis. These data indicate that WDR87 is located in the middle piece of the sperm tail and interacts with CFAP47 to form a complex which is involved in spermatozoa tail assembly.

Clinical detection, diagnosis and treatment of morphological abnormalities of sperm flagella: A review of literature

Sperm carries male genetic information, and flagella help move the sperm to reach oocytes. When the ultrastructure of the flagella is abnormal, the sperm is unable to reach the oocyte and achieve insemination. Multiple morphological abnormalities of sperm flagella (MMAF) is a relatively rare idiopathic condition that is mainly characterized by multiple defects in sperm flagella. In the last decade, with the development of high-throughput DNA sequencing approaches, many genes have been revealed to be related to MMAF. However, the differences in sperm phenotypes and reproductive outcomes in many cases are attributed to different pathogenic genes or different pathogenic mutations in the same gene. Here, we will review information about the various phenotypes resulting from different pathogenic genes, including sperm ultrastructure and encoding proteins with their location and functions as well as assisted reproductive technology (ART) outcomes. We will share our clinical detection and diagnosis experience to provide additional clinical views and broaden the understanding of this disease.

Potential role of dynein-related genes in the etiology of male infertility: A systematic review and a meta-analysis

BACKGROUND

The dynein-related genes may have a role in the etiology of male infertility, particularly in cases of impaired sperm motility.

OBJECTIVES

The goal of this review is to compile a list of the most important dynein-related candidate genes that may contribute to male factor infertility.

MATERIALS AND METHODS

Databases were searched using the keywords "dynein", "male", "infertility" and by applying strict inclusion criteria. A meta-analysis was also performed by using the eligible case-control studies. The odd ratios (OR), the Z-test score, and the level of significance were determined using a fixed model with a p value of 0.05. Funnel plots were used to check for publication bias.

RESULTS

There were 35 studies that met the inclusion criteria. There were a total of fifteen genes responsible for the production of dynein structural proteins, the production of dynein assembling factors, and potentially associated with male infertility. A total of five case-control studies were eligible for inclusion in the meta-analysis. Variants in the dynein-related genes were linked to an increased the risk of male infertility (OR = 21.52, 95% Confidence Interval (CI) 8.34 - 55.50, Z test = 6.35, p < 0.05). The percentage of heterogeneity, I² , was 47.00%. The lack of variants in the dynein genes was an advantage and this was statistically significant.

DISCUSSION

The results from the present review illustrate that pathogenic variants in genes both for dynein synthesis and for dynein assembly factors could be associated with isolated cases of male infertility without any other symptoms.

CONCLUSIONS

The genes addressed in this study, which are involved in both the production and assembly of dynein, could be used as molecular targets for future research into the etiology of sperm motility problems. This article is protected by copyright. All rights reserved.

Performance evaluation of differential splicing analysis methods and splicing analytics platform construction

A proportion of previously defined benign variants or variants of uncertain significance in humans, which are challenging to identify, may induce an abnormal splicing process. An increasing number of methods have been developed to predict splicing variants, but their performance has not been completely evaluated using independent benchmarks. Here, we manually sourced ∼50 000 positive/negative splicing variants from > 8000 studies and selected the independent splicing variants to evaluate the performance of prediction methods. These methods showed different performances in recognizing splicing variants in donor and acceptor regions, reminiscent of different weight coefficient applications to predict novel splicing variants. Of these methods, 66.67% exhibited higher specificities than sensitivities, suggesting that more moderate cut-off values are necessary to distinguish splicing variants. Moreover, the high correlation and consistent prediction ratio validated the feasibility of integration of the splicing prediction method in identifying splicing variants. We developed a splicing analytics platform called SPCards, which curates splicing variants from publications and predicts splicing scores of variants in genomes. SPCards also offers variant-level and gene-level annotation information, including allele frequency, non-synonymous prediction and comprehensive functional information. SPCards is suitable for high-throughput genetic identification of splicing variants, particularly those located in non-canonical splicing regions.

Novel compound heterozygous variants of DNAH17 in a Chinese infertile man with multiple morphological abnormalities of sperm flagella

Multiple morphological abnormalities of the sperm flagellum (MMAF) have been reported to be an important cause of male infertility and reflect a heterogeneous genetic disorder. Previous studies have identified dozens of candidate pathogenic genes for MMAF, but the aetiology in approximately 50% of cases remains unexplained. The present study aimed to identify novel potentially pathogenic gene variants of MMAF. A Chinese family with a 32-year-old infertile proband presenting with MMAF was recruited, and sperm morphology of the patient was examined by Papanicolaou staining. Whole exome sequencing was performed on the proband and Sanger sequencing was used to identify genetic variants in the family. The frequencies of variants were assessed using public databases and the effects on protein structure and function were predicted by online bioinformatics tools. The patient exhibited asthenozoospermia and a MMAF phenotype. Novel compound heterozygous variants (c.5368C > T, p.R1790C and c.13183C > T, p.R4395W) of the DNAH17 gene were identified in the patient, and showed autosomal recessive inheritance in this family. These variants were very rare in the GnomAD database. The two mutated amino acids were located in a highly conserved region of the DNAH17 protein. In silico analysis revealed that the compound heterozygous variants may compromise the function of DNAH17. Our findings expand upon the spectrum of pathogenic DNAH17 variants that are responsible for MMAF, and provide new knowledge for genetic counselling of male infertility due to MMAF.

LRRC46 Accumulates at the Midpiece of Sperm Flagella and Is Essential for Spermiogenesis and Male Fertility in Mouse

The sperm flagellum is essential for male fertility. Multiple morphological abnormalities of the sperm flagella (MMAF) is a severe form of asthenoteratozoospermia. MMAF phenotypes are understood to result from pathogenic variants of genes from multiple families including AKAP, DANI, DNAH, RSPH, CCDC, CFAP, TTC, and LRRC, among others. The Leucine-rich repeat protein (LRRC) family includes two members reported to cause MMAF phenotypes: Lrrc6 and Lrrc50. Despite vigorous research towards understanding the pathogenesis of MMAF-related diseases, many genes remain unknown underlying the flagellum biogenesis. Here, we found that Leucine-rich repeat containing 46 (LRRC46) is specifically expressed in the testes of adult mice, and show that LRRC46 is essential for sperm flagellum biogenesis. Both scanning electron microscopy (SEM) and Papanicolaou staining (PS) presents that the knockout of Lrrc46 in mice resulted in typical MMAF phenotypes, including sperm with short, coiled, and irregular flagella. The male KO mice had reduced total sperm counts, impaired sperm motility, and were completely infertile. No reproductive phenotypes were detected in Lrrc46-/- female mice. Immunofluorescence (IF) assays showed that LRRC46 was present throughout the entire flagella of control sperm, albeit with evident concentration at the mid-piece. Transmission electron microscopy (TEM) demonstrated striking flagellar defects with axonemal and mitochondrial sheath malformations. About the important part of the Materials and Methods, SEM and PS were used to observe the typical MMAF-related irregular flagella morphological phenotypes, TEM was used to further inspect the sperm flagellum defects in ultrastructure, and IF was chosen to confirm the location of protein. Our study suggests that LRRC46 is an essential protein for sperm flagellum biogenesis, and its mutations might be associated with MMAF that causes male infertility. Thus, our study provides insights for understanding developmental processes underlying sperm flagellum formation and contribute to further observe the pathogenic genes that cause male infertility.

A comparison of frozen-thawed embryo transfer protocols in 2920 single-blastocyst transfers

OBJECTIVE

To assess the effect of frozen-thawed embryo transfer (FET) protocol on live-birth rate (LBR) and clinical pregnancy rate (CPR), in single-vitrified-blastocyst transfer MATERIALS AND METHODS: Retrospective cohort study with FET of a single-blastocyst embryos (n = 2920 cycles) thawed 2013-2018. FET protocols were natural cycles (NC-FET) (n = 147), artificial hormone replacement treatment cycles (HRT-FET) (n = 2645), and modified NC (mNC) with hCG triggering (n = 128). Primary outcome was LBR. Adjustment for age, embryo grade, year of freezing\thawing, infertility cause, and endometrial thickness was performed.

RESULTS

There were no significant differences between the groups with regard to female age, embryo grade, and endometrial thickness. LBR was higher in the mNC compared to HRT-FET cycles (38.3% vs. 20.9% P < 0.0001), and in the NC compared to HRT-FET cycles (34.7% vs. 20.9%, P = 0.0002). CPR was higher in the mNC compared to HRT-FET cycles (46.1% vs. 33.3% P = 0.0003), and in the NC compared to HRT-FET cycles (45.9% vs. 33.3%, P = 0.002). There was no significant difference in LBR or CPR between NC-FET and mNC-FET. Higher LBR with NC-FET and mNC-FET remained significant after adjusting for confounders (aOR 2.42, 95%CI 1.53-3.66, P < 0.0001).

CONCLUSION

The use of the convenient artificial HRT-FET cycles must be cautiously reconsidered in light of the potential negative effect on LBR when compared with natural cycle FET.

Loss of function mutation in DNAH7 induces male infertility associated with abnormalities of the sperm flagella and mitochondria in human

Male infertility is an increasingly serious health problem affecting couples of reproductive age. Mutations in axoneme-associated genes cause male infertility. Dynein arm proteins are essential in sustaining normal axonemes and promote flagellar motility. However, the function of DNAH7 in male fertility in vivo remains unclear. Herein, we showed that DNAH7 disruption in humans results in male infertility, which was characterised by multiple morphological abnormalities of sperm flagella. The axoneme structure of the sperm from a DNAH7-deficient patient revealed the loss of inner dynein arms. Moreover, the mitochondria of the sperm flagella detached and dispersed outside the axoneme, leading to abnormalities in the mitochondrial sheath in the mid-piece region. Live birth was achieved via intracytoplasmic sperm injection. Thus, DNAH7 is critical for axoneme and mitochondrial development in human sperm. These findings further clarify the spectrum of DNAH7 biology and provide new insights for diagnosing infertility and treating patients harbouring DNAH7 mutations. This article is protected by copyright. All rights reserved.

Does increasing estrogen dose during frozen embryo transfer affect pregnancy rate?

OBJECTIVE

To assess the effect of increasing estrogen doses during hormone therapy frozen embryo transfer (HT-FET) cycles on endometrial thickness and success rates compared to patients who received fixed estrogen dose.

MATERIALS AND METHODS

A retrospective study from a university-based fertility clinic during the years 2008-2021. We compared two groups: the fixed-dose group (i.e., received 6 mg estradiol dose daily until embryo transfer) and the increased-dose group (i.e., the initial estradiol dose was 6 mg daily, and was increased during the cycle).

PRIMARY OUTCOME

clinical pregnancy rate.

RESULTS

The study included 5452 cycles of HT-FET: 4774 cycles in the fixed-dose group and 678 cycles in the increased-dose group. Ultrasound scan on days 2-3 of the cycle showed endometrial thickness slightly different between the two groups (4.2 mm in the fixed-dose and 4.0 mm in the increased-dose group, P = 0.003). The total estrogen dose was higher, and the treatment duration was longer in the increased than the fixed-dose group (122 mg vs. 66 mg and 17 days vs. 11 days, respectively; P < 0.001). The last ultrasound scan done before the addition of progesterone showed that the endometrial thickness was significantly thicker in the fixed than the increased-dose group (9.5 mm vs. 8.3 mm; P < 0.001). The clinical pregnancy rates were 35.8% in the increased-group vs. 34.1% in the fixed-dose group; P = 0.401.

CONCLUSIONS

The increased-dose group had thinner endometrium despite the higher doses of estrogen and longer treatment duration than the fixed-dose group. However, the pregnancy rates were similar between the two groups.