Serum antimüllerian hormone concentration increases with ovarian endometrioma size

The impact of ovarian endometrioma and endometriotic cystectomy on anti-Müllerian hormone, and antral follicle count: a contemporary critical appraisal of systematic reviews

Currently, three crucial questions regarding the reliability of ovarian reserve measures in women with ovarian endometrioma during the reproductive age are being discussed. Firstly, the effects of endometriotic cystectomy on short and long-term ovarian reserve. Secondly, the accuracy of serum anti-Müllerian hormone (AMH) and antral follicle count (AFC) in estimating ovarian reserve in these cases. Thirdly, the impact of endometrioma itself on the ovarian reserve over time in such cases. The purpose of the present review is to critically assess available systematic reviews and meta-analyses that have explored these questions. Nine eligible reviews were found following a systematic search on PubMed.com and similarly assessed. These reviews varied considerably regarding the level of evidence, as per an identical comprehensive scoring system. Moderate to high-quality evidence demonstrates that endometriotic cystectomy, by the stripping technique, adversely affects ovarian reserve in the short and long term, up to 9-18 months post-surgery. Damage to ovarian reserve was considerable but more pronounced in bilateral cases than unilateral cases, equivalent to 39.5% and 57.0%, respectively. Repeat endometriotic cystectomy is detrimental to ovarian reserve. The impact of endometrioma diameter on ovarian reserve before or after surgery is still unclear. Moderate to high-quality evidence, relying on simultaneous assessment of both ovarian reserve measures, shows that AMH is sensitive while AFC is not in cases undergoing ovarian cystectomy. AMH should be the biomarker of choice for counseling and managing women with endometrioma in their reproductive age, especially before surgery. While there is some evidence to show that endometrioma per se may harm ovarian reserve, this evidence is not robust, and there is good-quality evidence to challenge this notion. It is necessary to conduct further targeted RCTs, systematic reviews, and meta-analyses based on solid methodological grounds to increase the level of evidence, refine quantitative estimates, investigate open questions, and decrease heterogeneity.

Factors affecting the distribution of serum anti-müllerian hormone levels among infertile Asian women: a multi-nation, multi-centre, and multi-ethnicity prospective cohort study

STUDY QUESTION

How do age, ethnicity, and other characteristics affect serum anti-mullerian hormone (AMH) levels in Asian women undergoing fertility treatment?

SUMMARY ANSWER

Age, ethnicity, obesity (BMI ≥ 30 kg/m2), and polycystic ovarian syndrome (PCOS) significantly impacted serum AMH levels, with the rate of decrease accelerating as age increased; a concentration of 4.0 ng/ml was the optimal cut-off for diagnosis of PCOS.

WHAT IS KNOWN ALREADY

There are significant differences in ovarian reserve among women from different races and ethnicities, and Asian women often have poorer reproductive outcomes during assisted reproductive treatment cycles.

STUDY DESIGN, SIZE, DURATION

A population-based multi-nation, multi-centre, multi-ethnicity prospective cohort study of 4613 women was conducted from January 2020 to May 2021. Infertile women of 20-43 years of age were enrolled. The exclusion criteria included: age <20 or >43, non-Asian ethnicity, and missing critical data.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Participants were Asian women of Chinese, Japanese, Korean, Thai, Vietnamese, Malay, Indian, and Indonesian ethnicities from 12 IVF centres across Asia. These women were all naïve to ovarian stimulation cycles and attended IVF centres for fertility assessment. The AMH measurement was performed using an AMH automated assay on a clinically validated platform.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 4556 infertile Asian women were included in the final analyses. The mean ± SD for serum AMH concentrations (ng/ml) across specific age groups were: overall, 3.44 ± 2.93; age <30, 4.58 ± 3.16; 30-31, 4.23 ± 3.23; 32-33, 3.90 ± 3.06; 34-35, 3.21 ± 2.65; 36-37, 2.74 ± 2.44; 38-39, 2.30 ± 1.91; 40 and above, 1.67 ± 2.00. The rate of AMH decrease was ∼0.13 ng/ml/year in patients aged 25-33 and 0.31 ng/ml/year in women aged 33-43. The highest rates of PCOS were found in Indians (18.6%), Malays (18.9%), and Vietnamese (17.7%). Age (P < 0.001), ethnicity (P < 0.001), obesity (P = 0.007), PCOS (P < 0.001), and a history of endometrioma cystectomy (P = 0.01) were significantly associated with serum AMH values. Smoking status, pretreatment with GnRH agonist (GnRHa) or the oral contraceptive pill (OCP), freezing-thawing of blood samples, and sampling on Day 2 to Day 5 of the menstrual cycle or randomly did not appear to affect serum AMH levels. An AMH concentration of 4.0 ng/ml was the optimal cut-off for PCOS diagnosis with a sensitivity of 71.7% and specificity of 75.8% (AUC = 0.81, CI 95%: 0.79-0.83; P < 0.001).

LIMITATIONS, REASONS FOR CAUTION

The incidence of PCOS was supposedly high in this cohort as some IVF clinics were tertiary referral centres for managing specific fertility issues encountered by women with PCOS. Treatment with GnRHa or OCP before AMH testing was regionally and ethnically confined, mostly in Hong Kong SAR and Japan. Moreover, this reference for serum AMH value is limited to Asian women of the ethnicities examined and may not apply to other ethnicities not included in the study.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study to collate and construct age-specific reference ranges for serum AMH levels using the same bioassay on Asian women of different ethnicities. The findings of this investigation can assist clinicians to counsel and prognosticate about Asian women's ovarian reserve and reproductive potential, thus providing better strategies for personalized fertility interventions.

STUDY FUNDING/COMPETING INTEREST(S)

This study was technically supported by Ferring Pharmaceuticals and received no specific grant from any funding agency. All authors have no competing interests to disclose.

TRIAL REGISTRATION NUMBER

NCT04203355.

Impact of Laparoscopic Sclerotherapy for Ovarian Endometriomas on Ovarian Reserve

STUDY

Objective: To evaluate the impact of laparoscopic sclerotherapy on the management of endometrioma during surgery for deep infiltrative endometriosis (DIE).

DESIGN

Observational study.

SETTING

Tivoli-Ducos Clinic, Bordeaux.

PATIENTS

Sixty-nine patients underwent laparoscopic sclerotherapy for endometrioma during surgery for DIE.

INTERVENTIONS

Laparoscopic sclerotherapy with 95% ethanol solution and DIE surgery.

MEASUREMENTS AND MAIN RESULTS

Antimüllerian hormone (AMH) levels before and at least 6 months after surgery, recurrences, and pregnancies. Mean AMH (ng/mL) levels were 3.4 (2.3) before surgery and 2 (1.7) after surgery (p <.001). Mean difference was 1.29 ng/mL. Preoperative AMH level was the only variable independently associated with an additive decrease in AMH. Mean (standard deviation) follow-up period was 17.5 months (4.6) (range 9-26 months); 18 of 44 patients (40.1%) with pregnancy intent conceived. Of 51 patients who underwent postoperative pelvic ultrasound, 6 (6 of 51, 11.8%) had a recurrence of endometrioma.

CONCLUSION

Laparoscopic sclerotherapy for endometrioma >40 mm during surgery for DIE sclerotherapy has a low impact on AMH, preserves fertility, and prevents recurrence.

Endometrioma surgery-a systematic review and meta-analysis of the effect on antral follicle count and anti-Müllerian hormone

OBJECTIVE

Accurate preoperative counseling about whether an endometriotic cystectomy has a detrimental effect on the ovarian reserve has been a considerable challenge, because studies assessing the postoperative antral follicle counts and anti-Müllerian hormone levels have reported conflicting results. Our objective was to explore the impact of endometriotic cystectomy on both the anti-Müllerian hormone levels and antral follicle counts, with focus on prospective studies in which both variables were measured for each woman concurrently (overcoming unmeasured confounding), in the same setting (overcoming surgical technique differences), and at the same 3 postoperative time points, namely early (1-6 weeks), intermediate (2-6 months) and late (9-18 months), to overcome time-sensitive changes.

DATA SOURCES

Databases of PubMed, ClinicalTrials.gov, the Cochrane Library, Web of Science, and EBSCO were searched between January 2000 and October 2020.

STUDY ELIGIBILITY CRITERIA

Only prospective cohort studies that evaluated the impact of endometriotic stripping cystectomy on anti-Müllerian hormone levels and antral follicle counts in the same women, at matching time points, and in the same setting were eligible.

STUDY APPRAISAL AND SYNTHESIS METHODS

Two authors performed the screening and data extraction independently.

RESULTS

A total of 14 prospectively designed studies were eligible for the meta-analysis and included 650 women. The included studies had a low risk of bias. The postoperative weighted mean differences in serum anti-Müllerian hormone levels dropped significantly when compared with the preoperative levels by an estimated 1.77 ng/mL (95% confidence interval, 0.77-2.77; P<.001), 1.17 ng/mL (95% confidence interval, 0.66-1.67; P<.001), and 2.13 ng/mL (95% confidence interval, 1.61-2.65; P<.001) at the early (1-6 weeks), intermediate (2-6 months), and late (9-18 months) time points, respectively. This corresponded to a mean reduction in serum anti-Müllerian hormone levels at each of the 3-time points of 44.4%, 35.1%, and 54.2%, respectively. Conversely, the postoperative weighted mean difference in the antral follicle count estimates did not change significantly at any of the 3 time points; the early antral follicle count was 0.70 (95% confidence interval, -2.71 to 3.56; P=.63), the intermediate count was -0.94 (95% confidence interval, -2.53 to 0.65; P=.25), and the late count was 2.58 (95% confidence interval, -0.43 to 5.58; P=.09). Overall, high levels of heterogeneity were encountered (I² ranging between 92% and 94% for the anti-Müllerian hormone levels and between 94% and 98% for the antral follicle counts at the 3 time points), which were attenuated when similar anti-Müllerian hormone assays were compared, and the meta-regression suggested that age did not contribute to heterogeneity.

CONCLUSION

Endometriotic cystectomies are associated with a significant reduction in the serum anti-Müllerian hormone levels but not in the antral follicle counts, with the detrimental effects on the anti-Müllerian hormone levels consistently detectable at the early-, intermediate-, and late-postoperative time points. In women with endometrioma, the anti-Müllerian hormone level may provide a more accurate assessment of the risk for iatrogenic depletion of the ovarian reserve.

Anti-Müllerian hormone: A function beyond the Müllerian structures

The anti-Müllerian hormone (AMH) is a heterodimeric glycoprotein belonging to the TGFb superfamily implicated in human embryonic development. This hormone was first described as allowing regression of the epithelial embryonic Müllerian structures in males, which would otherwise differentiate into the uterus and fallopian tubes. It activates a signaling pathway mediated by two transmembrane receptors. Binding of AMH to its receptor induces morphological changes leading to the degeneration of Müllerian ducts. Recently, new data has shown the role played by this hormone on structures other than the genital tract. If testicular AMH expression decreases in humans over the course of a lifetime, synthesis may persist in other tissues in adulthood. The mechanisms underlying its production have been unveiled. The aim of this review is to describe the different pathways in which AMH has been identified and plays a pivotal role.

Anti-Müllerian Hormone in Female Reproduction

Anti-Müllerian hormone (AMH), also called Müllerian inhibiting substance, was shown to be synthesized by the ovary in the 1980s. This article reviews the main findings of the past 20 years on the regulation of the expression of AMH and its specific receptor AMHR2 by granulosa cells, the mechanism of action of AMH, the different roles it plays in the reproductive organs, its clinical utility, and its involvement in the principal pathological conditions affecting women. The findings in respect of regulation tell us that AMH and AMHR2 expression is mainly regulated by bone morphogenetic proteins, gonadotropins, and estrogens. It has now been established that AMH regulates the different steps of folliculogenesis and that it has neuroendocrine effects. On the other hand, the importance of serum AMH as a reliable marker of ovarian reserve and as a useful tool in the prediction of the polycystic ovary syndrome (PCOS) and primary ovarian failure has also been acknowledged. Last but not least, a large body of evidence points to the involvement of AMH in the pathogenesis of PCOS.

Fertility preservation for patients affected by endometriosis should ideally be carried out before surgery

RESEARCH QUESTION

What prognostic factors relate to a high oocyte yield in fertility preservation for women affected by endometriosis?

DESIGN

Observational cohort study conducted in a tertiary care university hospital between April 2015 and January 2019. Women who had undergone fertility preservation with ovarian stimulation for oocytes and embryo vitrification for endometriosis were included. Prognostic factors associated with the number of oocytes retrieved after the first ovarian stimulation were analysed.

RESULTS

A total of 146 women who had undergone 258 ovarian stimulation cycles were included; 82 (56.2%) had undergone more than one ovarian stimulation cycle; 72.6% had at least one endometrioma lesion; and 36.3% had previously undergone surgery for endometriosis. After adjustment by multiple linear regression, the factors that significantly reduced the number of oocytes retrieved were previous history of surgery for ovarian endometriosis (coefficient -1.08; 95% CI -2.02 to -0.15; P = 0.024); women's age (-0.21; 95% CI -0.41 to -0.01; P = 0.039); and total dose of gonadotrophin used (-0.01; 95% CI -0.01 to -0.00; P = 0.047). Anti-Müllerian hormone serum level and gravidity positively correlated with an increase in the number of oocytes retrieved (1.65; 95% CI 1.13 to 2.17; P < 0.001 and 3.30; 95% CI 0.91 to 5.68; P = 0.007, respectively) after the first ovarian stimulation cycle.

CONCLUSION

A history of surgery for ovarian endometriosis was associated with significantly lower oocyte yields. Fertility preservation should be integrated into endometriosis management. Fertility preservation should ideally be made available to the patient before surgery.

Ovarian function following use of various hemostatic techniques during treatment for unilateral endometrioma: A randomized controlled trial

OBJECTIVE

To compare the effect of hemostatic techniques (bipolar energy versus hemostatic sealants versus suture) on the ovarian reserve of patients submitted to laparoscopic cystectomy for the surgical excision of unilateral endometrioma.

METHODS

A randomized controlled trial conducted in a teaching hospital included 84 patients with unilateral endometrioma. The patients underwent laparoscopic stripping for excision of the unilateral endometrioma between March 2018 and February 2020. Three different hemostatic techniques-bipolar energy (Group 1), hemostatic sealants (Group 2), and suture (Group 3)-were compared. Anti-Müllerian hormone (AMH) levels were measured before, and 1 and 6 months after surgery to determine changes in ovarian function.

RESULTS

Following surgery, AMH levels decreased in all the groups; however, this decrease was not statistically significant. Comparison between groups showed no statistically significant differences in AMH levels between the three hemostatic techniques used. Six months after surgery, median AMH levels were: 1.65 ng/mL (interquartile range [IQR] 0.62-2.08 ng/mL) in Group 1, 1.87 ng/mL (IQR 1.27-2.97 ng/mL) in Group 2, and 1.53 ng/mL (IQR 1.18-2.44 ng/mL) in Group 3.

CONCLUSION

The present study suggests that there is no difference between the different hemostatic techniques used in laparoscopic cystectomy for the treatment of unilateral endometriomas. Registered at ClinicalTrials.gov: NCT03430609. https://clinicaltrials.gov/ct2/show/NCT03430609.

Pharmaceuticals targeting signaling pathways of endometriosis as potential new medical treatment: A review

Endometriosis (EM) is defined as endometrial tissues found outside the uterus. Growth and development of endometriotic cells in ectopic sites can be promoted via multiple pathways, including MAPK/MEK/ERK, PI3K/Akt/mTOR, NF-κB, Rho/ROCK, reactive oxidative stress, tumor necrosis factor, transforming growth factor-β, Wnt/β-catenin, vascular endothelial growth factor, estrogen, and cytokines. The underlying pathophysiological mechanisms include proliferation, apoptosis, autophagy, migration, invasion, fibrosis, angiogenesis, oxidative stress, inflammation, and immune escape. Current medical treatments for EM are mainly hormonal and symptomatic, and thus the development of new, effective, and safe pharmaceuticals targeting specific molecular and signaling pathways is needed. Here, we systematically reviewed the literature focused on pharmaceuticals that specifically target the molecular and signaling pathways involved in the pathophysiology of EM. Potential drug targets, their upstream and downstream molecules with key aberrant signaling, and the regulatory mechanisms promoting the growth and development of endometriotic cells and tissues were discussed. Hormonal pharmaceuticals, including melatonin, exerts proapoptotic via regulating matrix metallopeptidase activity while nonhormonal pharmaceutical sorafenib exerts antiproliferative effect via MAPK/ERK pathway and antiangiogenesis activity via VEGF/VEGFR pathway. N-acetyl cysteine, curcumin, and ginsenoside exert antioxidant and anti-inflammatory effects via radical scavenging activity. Natural products have high efficacy with minimal side effects; for example, resveratrol and epigallocatechin gallate have multiple targets and provide synergistic efficacy to resolve the complexity of the pathophysiology of EM, showing promising efficacy in treating EM. Although new medical treatments are currently being developed, more detailed pharmacological studies and large sample size clinical trials are needed to confirm the efficacy and safety of these treatments in the near future.

Does large endometrioma per se increase AMH level?

Women with endometriosis, especially those with endometrioma, present a considerable challenge for ovarian reserve appraisal. This diagnostic difficulty arises from several fundamental questions inherently linked to patient management: the potential influence of endometrioma on ovarian reserve; the adverse effect of ovarian surgery on ovarian reserve; and the adequacy of the established ovarian reserve biomarkers, anti-Müllerian hormone and antral follicle count, to appraise ovarian reserve accurately in these women. Until recently, a key argument was that the development and growth of endometriomas is associated with a progressive damage to normal ovarian tissue, resulting in a concomitant reduction in serum AMH levels. Contrary to this widely accepted position; recent studies have reported that, in women with no previous history of ovarian surgery, AMH levels were increased in women with large endometriomas. These findings are surprising and, if replicated, would have substantial clinical implications. In this commentary, we would, however, urge caution before these reports lead to systematic changes in clinical practice, and recommend urgent replication as the finding linking large endometrioma to high serum AMH levels seems to be biologically implausible, and contradicts the existing extensive body of research.

Impact of Surgical Management of Endometrioma on AMH Levels and Pregnancy Rates: A Review of Recent Literature

Ovarian endometrioma are found in up to 40% of women with endometriosis and 50% of infertile women. The best surgical approach for endometrioma and its impact on pregnancy rates is still controversial. Therefore, we conducted a literature review on surgical management of ovarian endometrioma and its impact on pregnancy rates and ovarian reserve, assessed by anti-Müllerian hormone (AMH) serum levels. Ovarian cystectomy is the preferred technique, as it is associated with lower recurrence and higher spontaneous pregnancy rate. However, ablative approaches and combined techniques are becoming more popular as ovarian reserve is less affected and there are slightly higher pregnancy rates. Preoperative AMH level might be useful to predict the occurrence of pregnancy. In conclusion, AMH should be included in the preoperative evaluation of reproductive aged women with endometriosis. The surgical options for ovarian endometrioma should be individualized. The endometrioma ablation procedure seems to be the most promising treatment.

Affected Ovary Relative Volume: A Novel Sonographic Predictor of Ovarian Reserve in Patients with Unilateral Endometrioma-A Pilot Study

BACKGROUND

The assessment of ovarian reserve in the case of endometrioma is of pivotal importance for planning a tailored management. However, both the antral follicle count (AFC) and the antimüllerian hormone (AMH) dosage are subject to a fair degree of variability in ovarian endometriosis. This study aimed to identify a sonographic parameter of ovarian reserve that could implement current available markers in patients with unilateral endometrioma.

METHODS

Patients with unilateral endometrioma admitted to our Endometriosis Center between March 2018 and April 2019 were enrolled. Transvaginal ultrasonography for the evaluation of eight sonographic indicators and AMH level determination were performed. The relationship between AMH level and each indicator was assessed.

RESULTS

Thirty-four women were included. There was a positive significant correlation between AMH level and the healthy ovary AFC (HO-AFC) (r = 0.36 p = 0.034). A stronger, negative correlation between AMH level and the ratio between the volume of the affected and the healthy ovary (affected ovary relative volume, AORV) (r = -0.47; p = 0.005) was evidenced. AORV had a satisfactory accuracy (AUC 0.73; CI 0.61-0.90; p = 0.0008), and the cut-off value of 5.96 had the best balance of sensitivity/specificity in distinguishing between patients with a good ovarian reserve (AMH ≥ 2 ng/mL) and those at risk of ovarian reserve depletion after excisional surgery.

CONCLUSION

AORV may be a useful tool to assess ovarian reserve in patients with unilateral endometrioma without previous surgery and to guide physicians in clinical management.

Endometrioma and reproductive issues: a well-informed patient may be the driver for change

Endometriosis affects a great proportion of women during their reproductive years and may impair female fertility in several ways. Ovarian endometrioma (OE) is the most frequent phenotype and growing evidence suggest an endometrioma-mediated damage to the ovary, ovarian reserve and oocyte quality. Traditionally, surgery has been the first-line treatment in cases of OE. Great advances in assisted reproduction and fertility preservation techniques opened new possibilities towards a more conservative approach. Herein we discuss multiple mechanisms responsible for the deterioration of the reproductive capacity in cases of OE as well as the pros and cons of different treatment options. The management of endometrioma-related subfertility remains controversial and it will depend on patient's intentions and priorities. In the "internet era" patients tend to be hyper-informed and more participative, but they are often misguided and misinformed. Thus, doctors should be able to convert these individuals into well-informed patients in order to facilitate the process of shared decision making, which is extremely relevant in the context of OEs.

Large ovarian endometriomas are associated with high pre-operative anti-Müllerian hormone concentrations

RESEARCH QUESTION

Are large ovarian endometriomas associated with high pre-operative anti-Müllerian hormone (AMH) concentrations?

DESIGN

Data from 332 women who underwent AMH measurement before surgery for endometriosis were prospectively recorded in a large database. Univariate analysis compared AMH concentrations in terms of the patients' baseline characteristics. A multivariate model was used to identify variables having an independent relationship with AMH concentration.

RESULTS

Among 332 women included in the study, 47.6% were aged 18-30 years, 67.8% were infertile and 85.5% were nulliparous. A total of 66.3% had ovarian endometriomas, and 10.8% had cysts measuring over 6 cm. Bilateral cysts over 3 cm were recorded in 24.7% of the women. Univariate analysis identified two variables that had a statistically significant relationship with AMH concentration: the woman's age (P = 0.01) and cyst size (P < 0.001). Multivariate analysis revealed that ages of 36-40 years and over 40 years showed a significant association with lower AMH concentrations (P = 0.02 and P = 0.009, respectively), while a cyst size of over 6 cm was statistically associated with high AMH concentrations (P < 0.001), after adjustment for smoking, parity, rectosigmoid endometriotic nodules and a bilateral location of endometriomas.

CONCLUSIONS

Pre-operative AMH concentration was significantly increased in women with large endometriomas of over 6 cm, independent of their age or the presence of bilateral endometriomas. This is relevant for both surgeons and patients when planning surgery in women with an intention to conceive post-operatively.

Do ovarian endometriomas affect ovarian response to ovarian stimulation for IVF/ICSI?

RESEARCH QUESTION

Does the presence of ovarian endometriomas affect ovarian response to ovarian stimulation after adjusting for age and ovarian reserve markers?

DESIGN

This retrospective cross-sectional study compared the ovarian response between patients with ovarian endometriomas and women with other infertility factors undergoing their first ovarian stimulation for IVF/intracytoplasmic sperm injection (ICSI). An age-specific nomogram model for the number of oocytes retrieved was built for both groups, and ovarian response was compared after adjusting for age, gonadotrophin dose, anti-Mullerian hormone (AMH) concentration and antral follicle count (AFC).

RESULTS

A total of 923 patients were included: 101 women with at least one ovarian endometrioma, and 822 patients with other infertility factors. Comparisons of the nomograms for the number of oocytes retrieved demonstrated that response was significantly lower for women with endometrioma when the results were adjusted for age the z-score for the number of oocytes retrieved (-0.49 ± 0.71 versus -0.20 ± 0.86; 95% confidence interval [CI] -0.47 to -0.12) and also after adjustment for the total dose of gonadotrophins and AMH values (z-score mean difference -0.338; 95% CI -0.54, -0.14). When the z-score was adjusted for gonadotrophin dose and AFC, the number of oocytes retrieved was comparable between the two groups (z-score mean difference -0.038; 95% CI -0.34 to 0.27).

CONCLUSIONS

Ovarian response after ovarian stimulation for IVF/ICSI in women with endometriomas is significantly lower than in controls after adjusting for age, gonadotrophin dose and AMH. Dose and protocol selection for ovarian stimulation in patients with endometrioma should be based on AFC rather than AMH, as the latter may be overestimated.