The potential for repeated ovulation and menstruation is thought to have provided a Darwinian advantage during the Palaeolithic. Reproductive conditions remained relatively stable until the pre-industrial era, characterized by late menarche, very young age at first birth, multiple pregnancies, and prolonged periods of lactational amenorrhoea. For hundreds of thousands of years, menstruators experienced few ovulatory cycles, even though they were genetically adapted to ovulate and menstruate every month. In the post-industrial era, the age at menarche gradually declined, the age at first birth progressively increased, and breastfeeding became optional and often of short duration. This created a mismatch between genetic adaptation and socio-environmental evolution, so that what was initially a probable reproductive advantage subsequently contributed to increased susceptibility to diseases associated with lifetime oestrogen exposure, such as ovarian, endometrial and breast cancer and, hypothetically, also those associated with the number of ovulatory menstruations, such as endometriosis and adenomyosis. The incidence of endometriosis shows a steep and progressive increase around the age of 25 years, but given the consistently reported delay in diagnosis, the actual incidence curve should be shifted to the left, supporting the possibility that the disease has its roots in adolescence. This raises the question of whether, from an evolutionary point of view, anovulation and amenorrhoea should not still be considered the physiological state, especially in the postmenarchal period. However, an increase in the frequency of endometriosis in recent decades has not been demonstrated, although this deserves further epidemiological investigation. In addition, as endometriosis occurs in a minority of individuals exposed to retrograde menstruation, other important pathogenic factors should be scrutinised. Research should be resumed to explore in more detail the transtubal reflux of not only blood, but also endometrial cells, and whether they are systematically present in the peritoneal fluid after menstruation. If repetitive ovulatory menstruation during the early reproductive years is shown to increase the risk of endometriosis and adenomyosis development and progression in susceptible individuals, hormonal interventions could be used as secondary prevention in symptomatic adolescents.

According to consistent epidemiological data, the slope of the incidence curve of endometriosis rises rapidly and sharply around the age of 25years. The delay in diagnosis is generally reported to be between 5 and 8years in adult women, but it appears to be over 10 years in adolescents. If this is true, the actual onset of endometriosis in many young women would be chronologically placed in the early postmenarchal years. Ovulation and menstruation are inflammatory events that, when occurring repeatedly for years, may theoretically favour the early development of endometriosis and adenomyosis. Moreover, repeated acute dysmenorrhoea episodes after menarche may not only be an indicator of ensuing endometriosis or adenomyosis, but may also promote the transition from acute to chronic pelvic pain through central sensitization mechanisms, as well as the onset of chronic overlapping pain conditions. Therefore, secondary prevention aimed at reducing suffering, limiting lesion progression, and preserving future reproductive potential should be focused on the age group that could benefit most from the intervention, i.e. severely symptomatic adolescents. Early-onset endometriosis and adenomyosis should be promptly suspected even when physical and ultrasound findings are negative, and long-term ovulatory suppression may be established until conception seeking. As nowadays this could mean using hormonal therapies for several years, drug safety evaluation is crucial. In adolescents without recognized major contraindications to oestrogens, the use of very low-dose combined oral contraceptives is associated with a marginal increase in the individual absolute risk of thromboembolic events. Oral contraceptives containing oestradiol instead of ethinyl oestradiol may further limit such risk. Oral, subcutaneous, and intramuscular progestogens do not increase the thromboembolic risk, but may interfere with attainment of peak bone mass in young women. Levonorgestrel-releasing intra-uterine devices may be a safe alternative for adolescents, as amenorrhoea is frequently induced without suppression of the ovarian activity. With regard to oncological risk, the net effect of long-term oestrogen–progestogen combinations use is a small reduction in overall cancer risk. Whether surgery should be considered the first-line approach in young women with chronic pelvic pain symptoms seems questionable. Especially when large endometriomas or infiltrating lesions are not detected at pelvic imaging, laparoscopy should be reserved to adolescents who refuse hormonal treatments or in whom first-line medications are not effective, not tolerated, or contraindicated. Diagnostic and therapeutic algorithms, including self-reported outcome measures, for young individuals with a clinical suspicion of early-onset endometriosis or adenomyosis are proposed.

Introduction: Peritoneal infiltrating and fibrotic endometriosis, also known as deep endometriosis, is the most severe manifestation of the disease that can cause severe complications including bowel and ureteral stenosis. The natural history of these lesions and the possible effect of hormonal treatments on their progression are undefined. Therefore, we conducted a systematic review and meta‐analysis to investigate whether and how frequently deep endometriosis progresses over time without or with ovarian suppression. This could inform management decisions in asymptomatic and mildly symptomatic patients.Material and Methods: For this pre‐registered systematic review (CRD42023463518), the PubMed and Embase databases were screened, and studies published between 2000 and 2023 that serially evaluated the size of deep endometriotic lesions without or with hormonal treatment were selected. Data on the progression, stability, or regression of deep endometriotic lesions were recorded as absolute frequencies or mean volume variations. Estimates of the overall percentage of progression and corresponding 95% confidence intervals were calculated using a random‐effect model. When studies reported lesion progression as pre‐ and post‐treatment volume means, the delta of the two‐volume means was calculated and analyzed using the inverse variance method.Results: A total of 29 studies were identified, of which 19 studies with 285 untreated and 730 treated patients were ultimately selected for meta‐analysis. The overall estimate of the percentage of lesion progression in untreated individuals was 21.4% (95% CI, 6.8–40.8%; I² = 90.5%), whereas it was 12.4% during various hormonal treatments (95% CI, 9.0–16.1%; I² = 0%). Based on the overall meta‐analysis estimates, the odds ratio of progression in treated vs untreated patients was 0.52 (95% CI, 0.41–0.66). During hormonal suppression, the mean volume of deep endometriotic lesions decreased significantly by 0.87 cm³ (95% CI, 0.19–1.56 cm³; I² = 0%), representing −28.5% of the baseline volume.Conclusions: Untreated deep endometriotic lesions progressed in about one in five patients. Medical therapy reduced but did not eliminate this risk. Given the organ function failure potentially caused by these lesions, the decision whether to use hormonal treatments in asymptomatic or mildly symptomatic women should always be shared, carefully weighing the potential benefits and harms of the two alternatives after extensive counseling.

STUDY QUESTION: Is it possible to reduce the cost of GnRH agonist treatment for endometriosis by using non-standard dosing regimens?SUMMARY ANSWER: An extended-interval dosing regimen of a 3.75 mg depot formulation of triptorelin injected every 6 weeks instead of every 4 weeks reduces the cost by one-third without compromising the effect on pain relief.WHAT IS KNOWN ALREADY: Cost constitutes a limit to prolonged GnRH agonists use. Alternative modalities to reduce the economic burden of GnRH agonist treatment have been anecdotally attempted.STUDY DESIGN, SIZE, DURATION: A systematic review was conducted to evaluate and compare the effect of three alternative modalities for GnRH use in women with endometriosis, i.e. intermittent oestrogen deprivation therapy, reduced drug dosage, and extended-interval dosing regimens of depot formulations. A PubMed and Embase search was initially conducted in October 2022 and updated in January 2023 using the following search strings: (endometriosis OR adenomyosis) AND (GnRH-agonists OR gonadotropin-releasing hormone agonists OR triptorelin OR leuprorelin OR goserelin OR buserelin OR nafarelin). Full-length articles published in English in peer-reviewed journals since 1 January 1980, and reporting original data on GnRH agonist treatment of pain symptoms associated with endometriosis were selected.PARTICIPANTS/MATERIALS, SETTING, METHODS: Information was extracted on study design, GnRH-agonist used, dosage, total duration of therapy, side effects, treatment adherence, and pelvic pain relief. Reviews, commentaries, conference proceedings, case reports, and letters to the editor were excluded.MAIN RESULTS AND THE ROLE OF CHANCE: Of the 1664 records screened, 14 studies regarding clinical outcomes associated with the 3 considered alternative modalities for GnRH agonist use were eventually included (intermittent oestrogen deprivation therapy, n = 2; low-dose or ‘draw-back’ therapy, n = 8; extended-interval dosing regimen, n = 4). Six studies were randomized controlled trials (RCTs) (double blind, n = 2) and eight adopted a prospective cohort design (non-comparative, n = 6; comparative, n = 2). A total of 776 women with endometriosis were recruited in the above studies (intermittent oestrogen deprivation therapy, n = 77; low-dose or ‘draw-back’ therapy, n = 528; extended-interval dosing regimen, n = 171). Robust data demonstrating cost saving without detrimental clinical consequences were available for the extended-interval dosing regimen only. In particular, the 3.75 mg triptorelin depot preparation inhibits ovarian function for a longer period compared with the 3.75 mg leuprorelin depot preparation, allowing injections every 6 instead of 4 weeks. Based on the cost indicated by the Italian Medicine Agency for the 3.75 mg triptorelin depot preparation, this would translate in a yearly saving of €744.60 (€2230.15–€1485.55; −33.4%).LIMITATIONS, REASONS FOR CAUTION: The quality of the evidence reported in the selected articles was not formally evaluated and a quantitative synthesis could not be performed. Some studies were old and the tested therapeutic approaches were apparently obsolete. Only cost containment associated with GnRH analogue use, and not cost-effectiveness, has been addressed.WIDER IMPLICATIONS OF THE FINDINGS: Consuming less resources without negatively impacting on health outcomes carries ethical and practical implications for individuals and the community, as this approach may result in overall increased healthcare access.STUDY FUNDING/COMPETING INTEREST(S): This study was supported by the Italian Ministry of Health (Ricerca Corrente 2023, IRCCS Ca' Granda Ospedale Maggiore Policlinico Milano). E.S. discloses payments from Ferring for research grants and honoraria from Merck-Serono for lectures. All other authors declare they have no conflict of interest.REGISTRATION NUMBER: N/A.

STUDY QUESTION: Are endometriotic lesions affecting bilateral organs or anatomical structures distributed symmetrically on both sides of the body? SUMMARY ANSWER: The left-sided preponderance of pelvic endometriotic lesions, and the right-sided dominance of thoracic and inguinal lesions, suggest that endometriotic lesions exhibit a non-random, asymmetric lateral distribution. WHAT IS KNOWN ALREADY: Evaluating the anatomical distribution of endometriotic lesions may elucidate the underlying pathogenic mechanism(s) of the disease. If the coelomic metaplasia or embryonic cell remnant theory is correct, a symmetrical right-left pattern would be expected. Conversely, retrograde menstruation would likely result in asymmetrical distribution, influenced by gravity, peritoneal fluid circulation, and anatomical niches. STUDY DESIGN, SIZE, DURATION: This systematic review with meta-analysis included full-length, English-language articles published up to 10 June 2024. Literature searches were performed in PubMed/Medline and Embase databases with the keyword ‘endometriosis’, ‘lateral’, ‘distribution’, ‘right’, ‘left’, and ‘asymmetry’. PARTICIPANTS/MATERIALS, SETTING, METHODS: The review focused on anatomical structures commonly affected by endometriosis with surgically defined right or left laterality: ovaries, uterosacral ligaments, colon, ureters, inguinal regions, and hemithorax (diaphragm, pleura, lungs). Case reports were excluded. Risk of bias was assessed using ROBINS-I for non-randomized studies and a dedicated tool for case series. Meta-analyses of proportions were conducted in R. Heterogeneity was quantified using the I2 statistic. Funnel plots for publication bias and Egger tests were performed using Stata. MAIN RESULTS AND THE ROLE OF CHANCE: Of 6356 articles screened, 154 met the inclusion criteria. A statistically significant left-sided preponderance was observed for ovarian (58%; 95% CI: 57–60%; P < 0.001), uterosacral ligament (56%; 95% CI: 54–59%; P < 0.001), ureteral (71%; 95% CI: 67–76%; P < 0.001), and bowel (72%; 95% CI: 64–79%; P < 0.001) lesions, whereas thoracic (98%; 95% CI: 96–100%; P < 0.001) and inguinal (92%; 95% CI: 83–98%; P < 0.001) lesions were predominantly right-sided. These findings were confirmed in the sensitivity analyses. Egger’s test indicated a possible small study effect only for ovarian lesions (P = 0.012). LIMITATIONS, REASONS FOR CAUTION: The preponderance of retrospective studies, the variability in surgical procedures, and the potential difficulties in accurately distinguishing unilateral from bilateral lesions may have influenced the magnitude of the estimated difference. However, the large patient cohorts, geographical diversity, and consistent asymmetry across lesion types strengthen the results’ validity and generalizability. WIDER IMPLICATIONS OF THE FINDINGS: The pattern of endometriotic lesion distribution, including the opposite asymmetry observed in the pelvis and upper abdomen/thorax, can be explained by factors influencing dissemination and implantation of refluxed endometrial cells. However, it cannot be explained as well by the coelomic metaplasia or embryonic cell remnant theories. This may have important clinical implications, providing a pathogenic basis for secondary prevention strategies. STUDY FUNDING/COMPETING INTEREST(S): The open access facility of this paper was funded by the Italian Ministry of Health, Current research IRCCS Ca’ Granda Ospedale Maggiore Policlinico. P.V. is a member of the Editorial Board of Human Reproduction Open, Journal of Obstetrics and Gynaecology Canada, and International Editorial Board of Acta Obstetricia et Gynecologica Scandinavica; has received royalties from Wolters Kluwer for chapters in UpToDate. All other authors declare no conflicts of interest. REGISTRATION NUMBER: CRD42024511356 (PROSPERO).

Purpose Although thoracic endometriosis (TE) represents the most common manifestation of extra-pelvic endometriosis, it is a rare condition and currently there is no established clinical guideline for the management of this condition. The study's primary objective was to assess patient satisfaction with the treatment provided. A secondary objective was to investigate the efficacy of different treatment modalities in terms of symptom and lesion recurrence. Methods A retrospective review of the clinical records of all women with TE who had been referred to our institution, a tertiary referral center, was conducted between January 2000 and September 2021. A frequency analysis was performed for all the variables examined in the study. The Kaplan–Meier method was adopted to analyse the time from thoracic surgery to PNX recurrence. Lastly, an intention-to-treat analysis was performed. Results Regarding clinical presentation, 50% of women (30/60; 95% CI 36.8–63.2) experienced at least one episode of pneumothorax (PNX). A total of 61.7% of the women in the study underwent surgical intervention, while 36.6% received pharmacological treatment. The cumulative recurrence rate of the first PNX following surgery was 0.26 (0.13–0.41) and 0.82 (0.44–0.95) at six months and 240 months, respectively. At the follow-up assessment, regardless of the administered treatment modality, over half of the women included in the study reported being satisfied with their treatment (PGIC). Additionally, most of them described their overall condition as having improved since the onset of the treatment (PGIS). Conclusion Both surgical and pharmacological treatments are valuable options for TE. Rather than being considered mutually exclusive, these approaches should be viewed as complementary.