Müllerian-Inhibiting Substance/Anti-Müllerian Hormone as a Predictor of Preterm Birth in Polycystic Ovary Syndrome

Anti-Mullerian Hormone and Fertility Treatment Decisions in Polycystic Ovary Syndrome: A Literature Review

Anti-Mullerian hormone is a robust marker of ovarian reserve and ovarian response in in vitro fertilisation (IVF). However, its role extends beyond improving the safety of IVF by aiding in choosing appropriate protocols and dosing. This review looks at the value of pre-treatment anti-Mullerian hormone (AMH) value in choosing the appropriate modality of treatment and its predictive ability for the outcomes of such treatment. It briefly addresses the factors that may modulate AMH levels and make clinical decision-making challenging.

Elevated antimüllerian hormone levels are not associated with preterm delivery after in vitro fertilization or ovulation induction

OBJECTIVE

To investigate the association between antimüllerian hormone (AMH) and preterm birth risk in a larger cohort of patients who underwent either in vitro fertilization or ovulation induction with intrauterine insemination at a US academic fertility center.

DESIGN

Retrospective cohort study.

SETTING

Single academic fertility center.

PATIENT(S)

Live singleton births from patients who underwent in vitro fertilization or ovulation induction between 2016 and 2020 at a single academic fertility center were included in this study. Patients were excluded if they had a missing prepregnancy AMH level, a pregnancy using donor oocytes or a gestational carrier, multiple gestations, a delivery before 20 weeks gestation, or a cerclage in place.

INTERVENTION(S)

AMH level.

MAIN OUTCOME MEASURE(S)

The primary outcome was the proportion of preterm delivery. Secondary outcomes included the rate of pregnancy-induced hypertension, gestational diabetes, and small for gestational age.

RESULT(S)

In the entire cohort (n = 875), 8.4% of deliveries were preterm. The mean AMH values were similar between those with term and preterm births (3.9 vs. 4.2 ng/mL). Similar proportions of patients with term and preterm deliveries had AMH levels greater than the 75th percentile (25% vs. 21%). The odds of preterm birth were similar by AMH quartile after adjusting for the history of preterm birth. Similarly, in the polycystic ovary syndrome (PCOS) cohort, there was no difference between mean AMH values of term and preterm births (n = 139, 9.6 vs. 10.0 ng/mL). The proportions of patients with PCOS with AMH levels greater than the 75th percentile were similar between those with term and preterm deliveries (25% vs. 22%). The odds of preterm birth were similar by the AMH quartile after adjusting for the history of preterm birth.

CONCLUSION(S)

Elevated AMH levels were not associated with an increased risk of preterm birth in patients who conceived after in vitro fertilization and ovulation induction, including patients with PCOS. Although studies suggest that AMH levels may help stratify the risk of preterm birth in this population, our findings indicate that further studies are needed before clinical application.

Association between serum AMH levels and IVF/ICSI outcomes in patients with polycystic ovary syndrome: a systematic review and meta-analysis

CONTEXT

Anti-Müllerian hormone (AMH) levels are increased in polycystic ovary syndrome (PCOS) patients and are associated with PCOS severity.

OBJECTIVE

To evaluate the associations between serum AMH levels and in vitro fertilization (IVF)/ intracytoplasmic sperm injection (ICSI) outcomes in patients with PCOS.

DATA SOURCES

PubMed, Embase, and the Cochrane Library were searched on 11 July 2022.

STUDY SELECTION

Studies reporting the association between serum AMH levels and IVF/ICSI outcomes in PCOS patients were considered for inclusion. The primary outcomes were clinical pregnancy, live birth, and ovarian hyperstimulation syndrome.

DATA EXTRACTION

Data were extracted using a standardized data extraction form. Study quality was assessed independently by two groups of researchers.

DATA SYNTHESIS

Nineteen studies were included in this review. Meta-analyses demonstrated that PCOS patients with a serum AMH level within the 75-100th percentile had a decreased odds of clinical pregnancy (OR: 0.77, 95% CI: 0.63-0.93) and livebirth (OR: 0.71; 95% CI: 0.58-0.87) compared to those within the 0-25th percentile. An increased AMH level was also correlated with an increased number of oocytes retrieved (SMD: 0.90, 95% CI: 0.30-1.51) and a lower odds of fertilization (OR: 0.92, 95% CI: 0.87-0.98). There was no significant difference in the number of MII oocytes (SMD: 1.85, 95% CI: -1.07-4.78), E2 on the day of hCG (SMD: 0.12; 95% CI: -0.98-1.23), or implantation (OR: 0.82, 95% CI: 0.28-2.39) between the two groups. In addition, we found significant dose-response associations between serum AMH level and clinical pregnancy, live birth, number of oocytes retrieved, and fertilization in PCOS patients.

CONCLUSION

AMH may have clinical utility in counseling regarding IVF/ICSI outcomes among women with PCOS who wish to undergo fertility treatment. More large-scale, high-quality cohort studies are needed to confirm these findings.

The impact of anti-Müllerian hormone on endometrial thickness in gonadotropin stimulation/intrauterine insemination cycles: is there an effect on pregnancy outcomes?

PURPOSE

To study the association, if any, between anti-Müllerian hormone (AMH) and pre-ovulatory endometrial thickness (ET) in gonadotropin/intrauterine insemination (IUI) cycles.

METHODS

This retrospective cohort study included a total of 964 patients undergoing 1926 gonadotropin/IUI cycles at an academic fertility center. Primary outcome measure was the association between serum AMH and measured ET on the day of and the day before human chorionic gonadotropin hormone (hCG) ovulation trigger. The effect of a model combining AMH and ET on early pregnancy outcomes was a secondary measure.

RESULTS

In 52.8% of cycles, ET was last assessed and recorded on the day of hCG administration, while in the remaining 47.2% on the day prior to trigger. In unadjusted regression models, AMH was weakly correlated with ET on hCG trigger day [bAMH (95%CI) = 0.032 (- 0.008, 0.070), p = 0.015]. When adjusting for potential confounders, the positive correlation became significant [0.051 (0.006, 0.102), p = 0.047]. Similar findings were observed when assessing the correlation between AMH and ET on the day prior to hCG trigger. ET was non-significantly associated with the odds of clinical pregnancy, when adjusting for potential confounders, except for when restricting the analysis to couples with idiopathic infertility [OR (95%CI), p-value: 0.787 (0.623, 0.993), 0.044].

CONCLUSION

Our findings support an effect of serum AMH on endometrial development in gonadotropin induced cycles, even when adjusting for the diagnosis of PCOS. ET was not associated with the odds of achieving a clinical pregnancy, except for couples with idiopathic infertility.

Role of anti-Mullerian hormone in polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most common gynecological endocrine disorders affecting up to 10% of all females in their reproductive age, and its cause of onset is still elusive. A spectrum of recent research reflected diverse associations between increased plasma level of anti-Mullerian hormone (AMH) and different clinical features of PCOS. Since AMH levels reflect the pool of growing follicles that potentially can ovulate, it can be stated that serum AMH levels can be used to assess the “functional ovarian reserve,” rather mentioning it as the “ovarian reserve.” AMH also appears to be a premier endocrine parameter for the assessment of atrophied ovarian follicular pool in response to age of individuals. AMH hinders the follicular development as well as the follicular recruitment and ultimately resulting in follicular arrest which is the key pathophysiologic condition for the onset of PCOS. Furthermore, FSH-induced aromatase activity remains inhibited by AMH that aids emergence of other associated clinical signs of PCOS, such as excess androgen, followed by insulin resistance among the PCOS individuals. Given the versatile association of AMH with PCOS and scarcity in literature explaining the underling mechanisms how AMH relates with PCOS, this review article will discuss the roles of AMH in the pathogenesis of PCOS which may introduce a new era in treatment approach of PCOS.

Different pregnancy outcomes according to the polycystic ovary syndrome diagnostic criteria: a systematic review and meta-analysis of 79 studies

OBJECTIVE

To correlate the distinct diagnostic criteria of polycystic ovary syndrome (PCOS) with the development of maternal and neonatal complications.

DESIGN

Systematic review and meta-analysis.

SETTING

Not applicable.

PATIENT(S)

Pregnant women with PCOS.

INTERVENTION(S)

Maternal and neonatal complications were compared among women with PCOS diagnosed with different criteria.

MAIN OUTCOME MEASURE(S)

The primary outcomes of gestational diabetes mellitus and preeclampsia (PE) were assessed for every diagnostic criterion.

RESULT(S)

Seventy-nine studies were included. Regarding gestational diabetes, the overall pooled prevalence was 14% (95% confidence interval [CI], 11%-18%; I², 97%), reaching the highest level when polycystic ovarian morphology on ultrasound and 1 of the remaining 2 Rotterdam criteria (1/2 Rotterdam criteria) were used (18%; 95% CI, 13%-24%; I², 20%) and the lowest when polycystic morphology on ultrasound and hyperandrogenism were used (3%; 95% CI, 0%-19%; I², not applicable). Regarding PE, the overall pooled prevalence was 5% (95% CI, 4%-7%; I², 82%). The highest PE prevalence was reported when the National Institutes of Health criteria were used (14%; 95% CI, 5%-33%; I², 90%) and the lowest when menstrual irregularities and 1 of the 2 Rotterdam criteria were used (2%; 95% CI, 1%-3%; I², not applicable).

CONCLUSION(S)

The prevalence of gestational diabetes mellitus in pregnant women with PCOS does not differ according to the criteria used; however, women diagnosed with PCOS per the National Institutes of Health criteria are at higher risk of PE.

Antimullerian Hormone Levels and Association with Abortion and Preterm Delivery in Patients with Polycystic Ovary Syndrome Who Conceived with Assisted Reproductive Techniques

Background

Pregnant PCOS patients were found to suffer from many adverse outcomes of pregnancy. Prediction of the fate of pregnancy and labor in PCOS patients was highly needed. There were recently discovered roles of serum AMH in those patients who were seeking for pregnancy and who were conceiving with assisted reproductive techniques.

Aim

To analyze the predictive roles of measuring serum levels of AMH in patients with PCOS who became pregnant spontaneously or used assisted reproductive techniques regarding abortion and preterm delivery.

Patients and Study Design

A total of 100 females with PCOS were included in the study and they underwent assisted reproductive techniques were included in the study and underwent measurement of AMH levels regularly.

Results

We found that a total of 70 patients had a term delivery, and 30 patients had a preterm delivery. We found no statistically significant differences between both groups regarding their age or body mass index (BMI). We showed that serum AMH levels were higher in the group of PCOS patients who had preterm delivery than in the group of patients with term delivery (p < .0.001).

Conclusions

High serum AMH levels were found to be associated with higher risks of occurrence of preterm labor in patients with PCOS who underwent assisted reproductive techniques. Our results gave a clue to clinicians for better management of the pregnancy process in these patients.

Elevated Anti-Müllerian Hormone Is an Independent Risk Factor for Preterm Birth Among Patients With Overweight Polycystic Ovary Syndrome

Objective

To explore whether elevated anti-Müllerian hormone (AMH) levels affect the rate of preterm birth (PTB) among PCOS patients with different BMIs.

Methods

In this retrospective cohort study, patients with PCOS who had undergone IVF/ICSI from January 2017 to December 2019 were included for potential evaluation. A total of 2368 singleton live births from PCOS patients were included. According to the BMI, all the PCOS patients were divided into two groups: BMI<24 kg/m2 and BMI≥24 kg/m2. In total, 1339 PCOS patients with a BMI<24 kg/m2 were grouped according to their serum AMH levels: ① <2.71 ng/ml (n=333), ② 2.71-4.08 ng/ml (n=330), ③ 4.09-6.45 ng/ml (n=351), and ④ >6.45 ng/ml (n=325). Additionally, 1029 cycles of patients with a BMI≥24 kg/m2 were grouped according to the serum AMH level: ① <2.71 ng/ml (n=255), ② 2.71-4.08 ng/ml (n=267), ③ 4.09-6.45 ng/ml (n=239), and ④ >6.45 ng/ml (n=268), with <2.71 ng/ml being considered the reference group. The grouping was based mainly on the interquartile range of serum AMH levels. The primary outcome of the study was PTB. The secondary outcomes were low birth weight (LBW), small for gestational age (SGA), macrosomia and large for gestational age (LGA).

Results

Regarding PCOS patients with a BMI<24 kg/m2, compared with the PTB rate of the AMH <2.71 ng/ml group, the PTB rates of the different groups were not significantly different (AMH 2.71-4.08, AOR (95% CI)=1.01 (0.52-2.00), P=0.99; AMH 4.09-6.45, AOR (95% CI)=0.93 (0.45-1.91), P=0.85; AMH>6.45, AOR (95% CI)=0.78 (0.35-1.73), P=0.54). Regarding PCOS patients with a BMI ≥24 kg/m2, compared with the PTB rate of the AMH <2.71 ng/ml group, the PTB rate of the AMH>6.45 ng/ml group was significantly higher (OR=2.47; 95% CI=1.34-4.55). After multiple logistic regression analysis, the risk of PTB in the AMH>6.45 ng/ml group was 2.1 times that in the AMH<2.71 ng/ml group (AOR=2.1, 95% CI=1.01-4.37, P=0.04). However, no statistically significant difference was found in the rate of SGA, LBW, macrosomia or LGA among patients in the different serum AMH groups.

Conclusion

For PCOS patients, a BMI≥24 kg/m2 plus serum AMH>6.45 ng/ml (75th percentile) is an independent risk factor for PTB.

Pregnancy outcome of freeze thaw cycles of polycystic ovary syndrome patients regarding the anti-Müllerian hormone percentile

Patients with polycystic ovary syndrome display increased levels of anti-Müllerian hormone. Frozen-thawed embryo transfer (FET) prevents ovarian hyperstimulation and results in better pregnancy outcome in PCOS patients. Therefore, we aimed to evaluate the effect of serum AMH levels on the pregnancy outcome of FET cycles in PCOS patients. 110 infertile women with PCOS who were recommended for embryo cryopreservation followed by FET. The patients' AMH levels were evaluated, and the age-related AMH percentiles were determined. The patients were then grouped according to AMH percentiles, namely, 75th-90th percentile (Group 1) and higher than the 90th percentile (Group 2).A total of 110 PCOS patients who conceived in Frozen Embryo Transfer (FET)-In-vitro Fertilisation (IVF) cycles were included in this study. The preterm delivery rates in FET cycles were higher in the group of PCOS patients with AMH levels greater than the 90th percentile than in patients in the 75th-90th percentile group (50% vs 28.8%, p = .024). In conclusion, PCOS patients with AMH levels higher than the 90^th percentile had substantially higher preterm delivery rates than those with AMH levels at the 75^th-90^th percentile, suggesting the need for closer follow-up. Further studies are needed to elucidate the underlying mechanisms behind this correlation.IMPACT STATEMENTWhat is already known on this subject? The association of AMH levels with the risk of adverse pregnancy outcomes has been previously investigated. In women with PCOS, substantially elevated AMH levels were significantly associated with preterm birth.What do the results of this study add? Results showed that the PCOS patients with higher AMH levels and underwent assisted reproductive treatment demonstrated an increased risk of preterm labour than the PCOS patients with lower AMH levels.What are the implications of these findings for clinical practice and/or further research? In women with PCOS, substantially elevated AMH levels were significantly related to preterm birth, suggesting the need for closer follow-up in this population and the need for further studies to elucidate the underlying mechanisms behind this correlation.

Pretreatment antimüllerian hormone levels and outcomes of ovarian stimulation with gonadotropins/intrauterine insemination cycles

OBJECTIVE

To evaluate the association, if any, between serum antimüllerian hormone (AMH) levels and probability of clinical pregnancy and spontaneous abortion (SAB) in the infertility setting.

DESIGN

Retrospective cohort study.

SETTING

Academic fertility center.

PATIENT(S)

A total of 1,861 gonadotropin stimulation/intrauterine insemination cycles stratified by AMH levels into 3 groups: Low, <25th percentile (<0.7 ng/mL); Middle, ≥25th and <75th percentile (0.7-4.4 ng/mL); and High, ≥75th percentile (≥4.5 ng/mL).

INTERVENTION(S)

Intrauterine insemination after stimulation with gonadotropins.

MAIN OUTCOME MEASURE(S)

Cumulative probability of clinical pregnancy over a maximum of 3 and/or 6 cycles and SAB incidence risk rate (IRR). The Kaplan-Meier failure function (log rank test), Cox proportional hazards models, and multilevel mixed-effects Poisson regression models were performed to compare outcomes among the AMH groups.

RESULT(S)

Overall, in both unadjusted and adjusted models, the probability of achieving a clinical pregnancy was higher in the Middle and High AMH groups compared with that in the Low AMH group, both over 3 (hazard ratios [95% confidence interval], 1.55 [1.05-2.29] and 1.85 [1.22-2.81], respectively) and 6 (1.71 [1.17-2.48] and 2.12 [1.42-3.16], respectively) cycles. In the unadjusted models, the SAB IRR was higher among the Low AMH group (IRR [95% confidence interval], 2.17 (1.11-4.24]), with the relationship persisting after adjusting for age (1.83 [0.93-3.60]). When the SAB IRR were calculated separately for the subpopulations with and without polycystic ovary syndrome, a similar relationship was noted among the latter in the unadjusted (1.94 [0.97-3.88]) and adjusted (1.74 [0.86-3.49]) analyses.

CONCLUSION(S)

In women undergoing gonadotropin stimulation/intrauterine insemination, AMH appears to affect the probability of achieving a clinical pregnancy. A possible negative impact, independent of age, on the risk of SAB was also suggested.

Endometrial function in women with polycystic ovary syndrome: a comprehensive review

BACKGROUND

Polycystic ovary syndrome (PCOS) is the most common cause of anovulatory infertility. An endometrial component has been suggested to contribute to subfertility and poor reproductive outcomes in affected women.

OBJECTIVE AND RATIONALE

The aim of this review was to determine whether there is sufficient evidence to support that endometrial function is altered in women with PCOS, whether clinical features of PCOS affect the endometrium, and whether there are evidence-based interventions to improve endometrial dysfunction in PCOS women.

SEARCH METHODS

An extensive literature search was performed from 1970 up to July 2020 using PubMed and Web of Science without language restriction. The search included all titles and abstracts assessing a relationship between PCOS and endometrial function, the role played by clinical and biochemical/hormonal factors related to PCOS and endometrial function, and the potential interventions aimed to improve endometrial function in women with PCOS. All published papers were included if considered relevant. Studies having a specific topic/hypothesis regarding endometrial cancer/hyperplasia in women with PCOS were excluded from the analysis.

OUTCOMES

Experimental and clinical data suggest that the endometrium differs in women with PCOS when compared to healthy controls. Clinical characteristics related to the syndrome, alone and/or in combination, may contribute to dysregulation of endometrial expression of sex hormone receptors and co-receptors, increase endometrial insulin-resistance with impaired glucose transport and utilization, and result in chronic low-grade inflammation, immune dysfunction, altered uterine vascularity, abnormal endometrial gene expression and cellular abnormalities in women with PCOS. Among several interventions to improve endometrial function in women with PCOS, to date, only lifestyle modification, metformin and bariatric surgery have the highest scientific evidence for clinical benefit.

WIDER IMPLICATIONS

Endometrial dysfunction and abnormal trophoblast invasion and placentation in PCOS women can predispose to miscarriage and pregnancy complications. Thus, patients and their health care providers should advise about these risks. Although currently no intervention can be universally recommended to reverse endometrial dysfunction in PCOS women, lifestyle modifications and metformin may improve underlying endometrial dysfunction and pregnancy outcomes in obese and/or insulin resistant patients. Bariatric surgery has shown its efficacy in severely obese PCOS patients, but a careful evaluation of the benefit/risk ratio is warranted. Large scale randomized controlled clinical trials should address these possibilities.

Follicular fluid anti-Müllerian hormone (AMH) concentrations and outcomes of in vitro fertilization cycles with fresh embryo transfer among women at a fertility center

PURPOSE

To enhance the understanding of the clinical significance of anti-Müllerian hormone (AMH) in follicular fluid, we aimed to determine the variability of AMH concentrations in follicular fluid within and across IVF cycles and whether high follicular fluid AMH concentrations are associated with improved clinical IVF outcomes.

METHODS

This was a retrospective cohort study of companion follicular fluid and serum samples from 162 women enrolled in the Environment and Reproductive Health (EARTH) Study between 2010 and 2016. AMH concentrations were quantified using a sandwich enzyme-linked immunosorbent assay. Spearman correlation and intra-class correlation (ICC) were calculated to assess variability of follicular fluid AMH, and generalized linear mixed models were used to evaluate the associations of FF AMH with IVF outcomes.

RESULTS

The median (interquartile range, IQR) age of the 162 women was 34.0 years (32.0, 37.0). Follicular fluid AMH concentrations were highly correlated between follicles within each IVF cycle (Spearman r = 0.78 to 0.86) and across cycles for each woman (ICC 0.87 (95% CI 0.81 to 0.92)). Compared with women in the highest tertile of FF AMH (mean AMH = 2.3 ng/ml), women in the lowest tertile (mean AMH = 0.2 ng/ml) had lower serum AMH (T1 = 0.1 ng/ml vs. T3 = 0.6 ng/ml, p < 0.0001). In adjusted models, higher tertiles of follicular fluid AMH concentrations were associated with lower mean endometrial thickness and higher probability of clinical pregnancy.

CONCLUSIONS

Follicular fluid AMH concentrations show little variability between pre-ovulatory follicles, and higher pre-ovulatory follicular fluid AMH may predict a higher probability of clinical pregnancy.

Highly elevated level of antimüllerian hormone associated with preterm delivery in polycystic ovary syndrome patients who underwent ovulation induction

OBJECTIVE

To determine the relationship between high antimüllerian hormone (AMH) levels and increased preterm delivery risk in populations of women with polycystic ovary syndrome (PCOS) or unexplained infertility undergoing ovulation induction.

DESIGN

Secondary analysis of data from two multicenter randomized clinical trials: Pregnancy in Polycystic Ovary Syndrome II (PPCOS II); and Assessment of Multiple Intrauterine Gestations from Ovarian Stimulation (AMIGOS).

SETTING

Not applicable.

PATIENTS

Live births at ≥24 weeks' gestation from both the PPCOS II (n = 172) and AMIGOS (n = 222) cohorts were evaluated, and those at risk for iatrogenic preterm delivery including placental conditions, fetal growth restriction, multiple gestations, hypertensive diseases of pregnancy, and pre-gestational diabetes were excluded. The final analysis included 118 women with PCOS from the PPCOS II cohort and 146 women with unexplained infertility from the AMIGOS cohort.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Spontaneous preterm delivery.

RESULTS

In the PCOS population, median AMH overall was 5.5 ng/dL (interquartile range 2.9-9.3 ng/dL). In all, 62% of participants who delivered preterm had AMH levels above the 75th percentile. When comparing clinical covariates between the preterm and term deliveries, women with PCOS who delivered preterm had notably higher AMH than their term counterparts (11.1 vs. 5.4 ng/mL). In the univariate logistic regression analysis, each unit increase in AMH raised the odds of preterm delivery by 14% (odds ratio 1.14, 95% confidence interval 1.02-1.26). The effect was magnified only after adjusting for age, race, body mass index, smoking status, testosterone, homeostatic model assessment for insulin resistance, and treatment randomization group (adjusted odds ratio 1.25, 95% confidence interval 1.06-1.49). Unlike in the PCOS population, the unexplained infertility cohort had no significant difference in AMH levels between those with or without preterm delivery (2.3 vs. 2.6 ng/mL).

CONCLUSIONS

Our findings suggest that women with PCOS and high AMH who conceived after ovulation induction represent a high-risk group for preterm delivery. These data indicate that closer monitoring in the third trimester of pregnancies in PCOS patients with early first trimester AMH levels above 9.3 ng/mL may be warranted.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01044862.

Single-cell sequencing of neonatal uterus reveals an Misr2+ endometrial progenitor indispensable for fertility

The Mullerian ducts are the anlagen of the female reproductive tract, which regress in the male fetus in response to MIS. This process is driven by subluminal mesenchymal cells expressing Misr2, which trigger the regression of the adjacent Mullerian ductal epithelium. In females, these Misr2+ cells are retained, yet their contribution to the development of the uterus remains unknown. Here, we report that subluminal Misr2+ cells persist postnatally in the uterus of rodents, but recede by week 37 of gestation in humans. Using single-cell RNA sequencing, we demonstrate that ectopic postnatal MIS administration inhibits these cells and prevents the formation of endometrial stroma in rodents, suggesting a progenitor function. Exposure to MIS during the first six days of life, by inhibiting specification of the stroma, dysregulates paracrine signals necessary for uterine development, eventually resulting in apoptosis of the Misr2+ cells, uterine hypoplasia, and complete infertility in the adult female.

In the womb, mammals possess all of the preliminary sexual structures necessary to become either male or female. This includes the Mullerian duct, which develops into the Fallopian tubes, uterus, cervix, and vagina in female fetuses. In male fetuses, the testis secretes a hormone called Mullerian inhibiting substance (MIS). This triggers the activity of a small group of cells, known as Misr2+ cells, that cause the Mullerian duct to degenerate, preventing males from developing female sexual organs.

It was not clear what happens to Misr2+ cells in female fetuses or if they affect how the uterus develops. Saatcioglu et al. now show that in newborn female mice and rats, a type of Misr2+ cell that sits within a thin inner layer of the developing uterus still responds to MIS. At this time, the uterus is in a critical early period of development. Treating the mice and rats with MIS protein during their first six days of life eventually caused the Misr2+ cells to die. The treatment also prevented a layer of connective tissue, known as the endometrial stroma, from forming in the uterus. As a result, the mice and rats were infertile and had severely underdeveloped uteri.

While the Misr2+ cells are present in newborn rats and mice, Saatcioglu et al. found that they disappeared before birth in humans. However, the overall results suggest that Misr2+ cells act as progenitor cells that develop into the cells of the endometrial stroma. Future work could investigate the roles these cells play in causing uterine developmental disorders and infertility disorders. Furthermore, the finding that MIS inhibits the Misr2+ cells could help researchers to develop treatments for uterine cancer and other conditions where the cells of the uterus grow and divide too much.