{"paper_id":"a3ca6515-49ef-4626-9a7d-a7885f999ff1","body_text":"REVIEW | OPEN ACCESS   \n \nMedical Science 30, e112ms3921 (2026)                                                                                                                                                               1 of 11 \n \n N-acetylcysteine as an \nInvestigational Molecular Modulator \nin Endometriosis: A Narrative \nReview  \n \nMagdalena Rakuś1*, Krzysztof Łukasz1, Jakub Marzec1, \nMichał Nowakowski1, Aleksandra Musioł1, Paweł Gwałt1 \n  \n \n \nABSTRACT \nBackground: Endometriosis is an inflammatory condition featuring persistent \noxidative stress. Usual hormonal therapy and surgery can be limited because they \nintroduce contraceptive effects. Aim: This review considers the potential of N -\nacetylcysteine (NAC) as a candidate non -hormonal molecule that could influence \nendometriosis, while considering the preliminary and methodological weaknesses \nof the available data. Materials and Methods: A structured PubMed-MEDLINE search \n(January 2010 – May 2026) was performed to identify the role of N -acetylcysteine \n(NAC) in endometriosis. A comparative approach was used to summarize the \nmethodological validity of preclinical animal studies and clinical trials and to assess \nstudy quality. Results: Evidence from mechanistic studies and experimental models \nindicates NAC as a candidate factor associated with molecular changes in tissue \nand lesion regression in preclinical models. Clinical research reports pain relief and \na reduction in endometrioma size; however, the results are affected by small sample \nsizes, lack of randomization and placebo control, or mixed antioxidant \nformulations. Conclusions: Current knowledge is insufficient to support NAC as a \nconventional treatment for endometriosis. Limitations stemming from the heavy \nreliance on preclinical models and the confounding design of clinical trials hinder \nunderstanding of NAC’s role. Further research needs to focus on randomized \ncontrolled trials on NAC alone. Showing the disease -modifying potential of NAC \nrequires long-term outcomes. \n \nKeywords: endometriosis, n-acetylcysteine (NAC), redox signaling modulation, \nproliferation-to-differentiation switch \n \n \n \n1. INTRODUCTION  \nBackground \nEndometriosis represents an estrogen -dependent chronic illness characterized by \nthe proliferation of endometrium -like lesions and/or stroma beyond the \nendometrium and myometrium (Tomassetti et al., 2021). The pathogenesis of this \ndisease involves chronic inflammation, in which reactive oxygen species (ROS) \nproduction exceeds antioxidant defenses, leading to oxidative stress (Clower et al., \nMedical Science \n \nTo Cite: \nRakuś M, Łukasz K, Marzec J, Nowakowski M, Musioł A, Gwałt P. N-\nacetylcysteine as an Investigational Molecular Modulator in \nEndometriosis: A Narrative Review. Medical Science 2026; 30: \ne112ms3921 \ndoi: https://doi.org/10.54905/disssi.v30i172.e112ms3921  \n \nAuthors’ Affiliation: \n1Medical University of Warsaw; ul. Żwirki i Wigury 61, 02-091 Warsaw, \nPoland \n \n⃰ Corresponding author: \nMagdalena Rakuś, \nMedical University of Warsaw; ul. Żwirki i Wigury 61, 02-091 Warsaw, \nPoland, \nE-mail: magdarakus@gmail.com; phone number: +48883147626 \n \nContact list: \nMagdalena Rakuś:  magdarakus@gmail.com \nKrzysztof Łukasz:  k9lukasz@gmail.com \nJakub Marzec:  kuba84848@gmail.com \nMichał Nowakowski:  nowakowski_@outlook.com \nAleksandra Musioł:  s082601@student.wum.edu.pl \nPaweł Gwałt:  pawel.gwt@gmail.com \n \nORCID List: \nMagdalena Rakuś  0009-0008-9301-6680 \nKrzysztof Łukasz  0009-0002-3438-1967 \nJakub Marzec  0009-0003-4096-543X \nMichał Nowakowski  0009-0004-9113-4780 \nAleksandra Musioł  0009-0000-0495-2146 \nPaweł Gwałt   0009-0005-3163-9696 \n \nPeer-Review History \nReceived: 07 May 2026 \nReviewed & Revised: 15/May/2026 to 16/June/2026 \nAccepted: 21 June 2026 \nPublished: 29 June 2026 \n \nPeer-review Method \nExternal peer-review was done through double-blind method. \n \nMedical Science \npISSN 2321–7359; eISSN 2321–7367 \n \n \n© The Author(s) 2026. Open Access. This article is licensed under a Creative Commons \nAttribution License 4.0 (CC BY 4.0)., which permits use, sharing, adaptation, distribution and \nreproduction in any medium or format, as long as you give appropriate credit to the original \nauthor(s) and the source, provide a link to the Creative Commons license, and indicate if \nchanges were made. To view a copy of this license, visit \nhttp://creativecommons.org/licenses/by/4.0/. \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \nDISCOVERY \nSCIENTIFIC SOCIETY \n \n\n \nREVIEW | OPEN ACCESS   \n \nMedical Science 30, e112ms3921 (2026)                                                                                                                                                               2 of 11 \n2022). Endometriosis occurs in women of reproductive age all around the world, with a prevalence rate of around 10%. It is kn own to \nimpact health through symptoms of chronic pelvic pain, dysmenorrhea, dyspareunia, dyschezia, dysuria, and infertility (Zonder van et \nal., 2020). This pathology negatively impacts psychological health and is associated with disruption of the education and emp loyment \nopportunities (Facchin et al., 2026). \n \nCurrent Clinical Guidelines and Standard of Care \nAt the moment, endometriosis cannot be completely cured (As-Sanie et al., 2025). Treatment strategy includes symptom control and the \nprevention of recurrence. According to the ESHRE guidelines of 2022, a combination of hormonal contraceptives is recommended for \nmanaging pain, while progestins act as second -line medications for controlling pain and promoting fertility. GnRH agonists and \nantagonists should be used after other treatment options fail. Another treatment pillar involves surgery with a predilection towards \nlesions excision and cystectomy, with post -surgical hormone suppression being necessary unless pregnancy is sought by a woman \n(Becker et al., 2022). It is essential to emphasize that N -acetylcysteine (NAC) described in the current review is not a part of any \ntreatment protocol and is not recommended as for now. \n \nUnmet Medical Need and Treatment Gap \nA serious problem associated with the majority of currently available hormonal treatment options is the fact that the mechanism behind \nthese medicines consists of blocking ovulation. As a consequence, these methods are contraception methods and cannot be \nadministered to those women who wish to conceive (Taylor et al., 2021). The recurrence rate is high when a patient does not r eceive \nhormone suppression after surgery (Veth et al., 2024). Moreover, some surgical approaches have been shown to deplete ovarian reserve \n(Li et al., 2026). Thus, a medical gap arises due to the necessity of non -hormonal drug development that will stop disease progression \nwhile not affecting reproductive capabilities. \n \nResearch Objective  \nThe current narrative review evaluates the potential of N-acetylcysteine (NAC) as a model for experimental research into the molecular \nregulation of endometriosis. Specifically, the aim of the present research aims to discuss the opportunities for developing a  non-\nhormonal model that facilitates stabilization of the disease progression without affecting hormones.  At the same time, given  that the \nmajority of scientific work addressing the problem in question consists of in vitro and preclinical research, this review focuses on this \nimportant issue. \n \n2. REVIEW METHODS \nSearch Strategy \nTo get a picture of how NAC could affect endometriosis, a thorough review of the PubMed/MEDLINE database was performed. The \ntimeline for the literature search was set from January 2010 to May 2026. The process relied on a combination of Medical Subj ect \nHeadings (MeSH) terms: (“endometriosis” OR “endometrioma”) AND (“N-acetylcysteine” OR “NAC” OR “N-Acetyl cysteine”). \n \nSelection Criteria \nThe inclusion criteria targeted research analyzing NAC as an intervention in the endometriosis model system or as an important factor \nto be considered in studies involving the disease. As a consequence of a gap in current therapies, parameters of interest inc luded \noxidative environmental changes, alterations in lesion size, pain scores, and reproductive performance. Studies investigating  \nmonotherapy were chosen to isolate the modulatory effect of NAC directly; however, multicomponent antioxidative studies were \nincluded as well to examine the antioxidative capabilities of the compound. During the initial screening stage, reviews and m eta-\nanalyses were excluded. During the eligibility assessment, papers related to other pathologies, treatments, hormonal manipula tions, \nand other unrelated matters were excluded, resulting in the selection of 14 papers for the review. For presentation purposes and to \nensure methodological transparency, a PRISMA flowchart was created (Figure 1). \n \n \n \n \n\n \nREVIEW | OPEN ACCESS   \n \nMedical Science 30, e112ms3921 (2026)                                                                                                                                                               3 of 11 \n \n \nFigure 1. PRISMA flow chart \n \nData Extraction and Synthesis \nNarrative synthesis was applied. Given the exploratory character of current research and the heterogeneity of approaches used  in \nrelevant papers, a critical analysis of methodology was conducted for each study. The synthesis focused on quality, methodolo gical \naspects, and risk of bias in preclinical models and clinical trials to isolate NAC's molecular efficacy. \n \n3. RESULTS \nStudy Findings: Murine Model \nA possible “proliferation -to-differentiation switch” mechanism was first tested in a group of 40 mice, in which NAC administration \nreduced endometrioma mass by 60% compared with untreated controls. The regression was observed due to the antiproliferative \neffect, characterized by a decrease in the proliferation marker Ki -67, from 1.88±0.28% in the untreated animals to 0.87±0.11% ( P < 0.01). \nIt seems that NAC induced differentiation and maturation processes, as reflected by E -cadherin localization at cell junctions rather than \nin the cytoplasm, with a 67% increase in the junctional protein compared with controls. This effect corresponded to the lower  motility \nand invasiveness of the endometriotic cells. Moreover, the treatment reduced cyclooxygenase -2 (Cox2) mRNA expression and inhibited \nmatrix metalloproteinase-9 (MMP-9) activity by more than 60%. Thus, NAC targets inflammation and invasive processes characteristic \nof this pathology. The described findings provide the basis for this mechanism, but they are still only the first stage of ex perimental \nstudies, since it is necessary to account for the specific microenvironment of human organisms when translating findings from  animal \nexperiments into practice (Pittaluga et al., 2010). \n\n\n \nREVIEW | OPEN ACCESS   \n \nMedical Science 30, e112ms3921 (2026)                                                                                                                                                               4 of 11 \n \nClinical Observations: Results in Non-Randomized Populations \nThe efficacy of N -acetylcysteine (NAC) therapy in the clinical practice of endometriosis among 92 patients, 47 treated and 45 controls \nwithout the drug administration, has been evaluated using ultrasound diagnosis of endometriomas. To optimize pharmacokinetics , a \n“pulse therapy” was utilized: NAC was given three times per day at 600 mg, resulting in an overall intake of 1.8 g/day for th ree days a \nweek, followed by a four -day medication-free period. During three months of observations, a minimal 1.5 mm reduction in cyst size in \ntreated patients was observed, compared with a 6.6 mm increase in untreated patients (P = 0.001). While the discussed study is useful to \ntransfer the findings from laboratory animals to the clinical setting, its methodology bears certain restrictions due to the relatively low \nnumber of patients ( n = 92) involved in the research process, as well as due to the rather brief observation period (3 months), which is \nnot sufficient to determine the durability of the effects observed. The investigation reported 24 operations canceled because  of \nsymptom remission: dysmenorrhea (55%, P = 0.001), dyspareunia (50%, P = 0.027), and chronic pelvic pain (59%, P = 0.015). Without a \nplacebo control, it is impossible to distinguish the drug's physiological effect from placebo-related changes in subjective complaints.  \nA morphologically differentiated epithelium and higher expression levels of junctional proteins like E -cadherin and β-catenin have \nbeen identified in treated lesions. A simultaneous decrease in the COX-2 expression has also been established. It could explain cyst \nregression via the hypothesized mechanism, which includes lower Prostaglandin -E2 (PGE2) production, thereby decreasing the \nstimulation of aromatase activity and estrogen formation.  The immunohistochemical approach to confirm the identified biochemical \nmechanisms has been carried out by the authors on 4 cyst samples taken from the operated patients (laparoscopy) to avoid poss ible \nconfounding factors. The described research findings are prone to selection bias, since the assignment of patients to the con trol and \ntreatment groups depended on their willingness to undergo NAC administration. In addition, the study's one -site design limits its \nexternal validity (Porpora et al., 2013). \n \nSymptom Evaluation: Prospective Single-Arm Data \nProspective research involving 120 female subjects demonstrated the clinical efficacy of the 3 -day NAC pulse therapy protocol. It was \nreported that there was a decrease in physical lesions, as the mean cyst diameter went down from 36. 5 ± 25.4 mm to 33.0 ± 23.5 mm \nduring three months (P < 0.001). Nevertheless, given the significant Standard Deviation and the lack of a control group, one can see the \npreliminary nature of the results. The number of patients involved in the research does not represent an adequate sample size  \nconsidering the widespread occurrence and different types of the disease. The period of three months seems to be too short to  evaluate \nthe long -term effects of such a chronic and recurrent disorder. Concurrent changes include both lowering serum cancer antigen \n(CA125) (45.5 U/mL to 35.6 U/mL; P = 0.001) and body mass index (BMI) of the participants (22.2 to 21.2 kg/m 2). Those changes seem to \nreflect the anti-inflammatory properties of NAC rather than lesion-specific effects and cannot be attributed solely to the drug.  \nManagement of clinical symptoms has resulted in lower Visual Analog Scale (VAS) scores for dysmenorrhea (6.9 to 4.8; P < 0.0001) \nand chronic pelvic pain (7.2 to 5.7; P < 0.001), as well as decreased need for NSAID usage. A single -arm design does not allow \nevaluation of the intervention's efficacy relative to the control group, making the conclusions questionable. In addition, th ere is a high \nlevel of uncertainty related to reproduction outcomes, as only 39 out of 52 patients conceived spontaneously within six month s. Since \nthe researchers have noted a decrease in dyspareunia, it is quite challenging to differentiate between cellular receptiveness  and \nbehavioral changes, as increased sexual activity might have been the consequence of less pain. Therefore, biological efficacy  requires \nverification in future RCTs (Anastasi et al., 2023). \n \nIFN-γ Synergy and Programmed Organelle Failure: In Vitro Mechanisms \nAn in vitro  approach aimed at elucidating the molecular mechanisms underlying the proposed molecular switch, using human \nendometriotic ( 12Z) and endometrial ( HESC) stromal cell lines. Consequently, these outcomes cannot be translated clinically and \nrequire validation in human -derived tissue. Therefore, the results of this work can only be validated clinically for human tissue \nsamples and cannot yet be applied clinically. This research revealed that NAC’s activity is dependent on the immune milieu, \ndemonstrating a cooperative effect with Interferon -gamma ( IFN-γ) in inhibiting cell proliferation. While they each inhibited cell \nproliferation, their combination led to the production of antiproliferative effects by inducing mitochondrial dysfunction and  ER stress, \nas evidenced by elevated levels of p -IRE1-α. A combined analysis strategy, comprising xCELLigence  (real-time cell impedance \nanalyses) assays, flow cytometry, immunofluorescence staining, western blotting, and metabolomics analysis, gave a detailed \nunderstanding of the molecular processes driving this disturbance of energy pathways in cells.  \n\n \nREVIEW | OPEN ACCESS   \n \nMedical Science 30, e112ms3921 (2026)                                                                                                                                                               5 of 11 \nThe data revealed that it leads to cell starvation and organellar dysfunction, where p -IRE1-α acts as a mediator of this process, \nwhich makes it a possible therapeutic or prognostic target. Despite these advances, this study was limited by the use of immo rtalized \ncell lines, such as 12Z and HESC, which exhibit characteristics similar to cancerous cells and may therefore lead to increased metabolic \nchanges. Additionally, NAC did not exert any effects on cytokine -induced cell proliferation, like IL -6, or TNF -α, showing that its \ntherapeutic utility may be limited to specific inflammatory profiles rather than serving as a universal intervention (Karakoç et al., 2025). \n \nSystemic Immunomodulation and Regression of Endometriotic Lesions \nThe in vivo  efficacy of systemic N -acetylcysteine (NAC) was compared with current pharmaceutical options in a randomized \nexperiment in rats using surgically induced endometriosis. The findings indicated that NAC administration after 3 weeks reduc ed the \naverage size of endometrial ectopic lesions (61.2±57.9 mm 2 to 30.5±21.9 mm 2; P = 0.043). While this treatment showed competitive \nperformance to leuprolide acetate, causing a reduction in lesion size (44.3±43.5 mm 2 to 19.6±20.0 mm 2; P = 0,008) as well as amifostine  \n(30.8±16.4 mm2 to 18.7±15 mm2; P = 0.012), no changes were observed in the control group. Apart from lesion structural diminishment, a \ndecrease in levels of TNF-α was detected both in systemic (41.7±9.9 pg/mL to 17.25±10.1 pg/mL; P = 0.01) and peritoneal fluid (37.5±15.3 \npg/mL to 19.2±13.1 pg/mL; P = 0.06) within NAC -, amifostine - and leuprolide -treated groups. Although this experiment exhibited \npromising results, there are limitations to its generalizability. First, rodents with surgically induced endometriosis do not  replicate the \ncomplex immune pathology seen in humans, and second, since the treatment lasted only three weeks, there is a probability of \nendometriosis recurrence, or withdrawal of improvements in chronic clinical signs of pelvic pain and infertility (Onalan et al., 2014). \n \nModulation of Autophagy in Endometriotic Lesions \nAnother piece of literature shows that N -acetylcysteine (NAC) regulates defective autophagy in ectopic endometrium via inhibiting \nreactive oxygen species (ROS). Using a surgically induced rat model (n = 40), investigators discovered that the endometriosis-associated \ninflammatory and oxidative environment elevates ROS, which stimulates the expression of certain autophagy proteins, such as \nmicrotubule-associated protein light chain 3 (LC3), and Beclin -1. Injection of the peritoneum with NAC (200 mg/kg) for 21 days \nreduced oxidative stress and subsequently inhibited both LC3 fluorescence and Beclin -1 protein expression. This effect of NAC is \nrelated to interference with the connection between ROS and autophagy. It helps avoid ongoing oxidative damage and supports c ell \nsurvival strategies, thereby leading to lesion proliferation. However, the use of the surgically induced rat model is limited  by its lack of \ntranslational potential, because suturing uterine tissue cannot repeat the multifactorial pathogenesis of endometriosis in hu mans. \nAdditionally, the small number of animals per subgroup ( n = 10) shows variability, and the relatively short treatment period makes it \nchallenging to extrapolate results (Lu et al., 2020). \n \n3D Spheroid Modeling and Glutathione Exhaustion under NAC Interventions \nModern in vitro studies have moved to 3D modeling to more accurately simulate metabolic stress. As part of this research, 3D tissue -\nlike models were created from biopsies of human endometriosis lesions, 12Z cells, and Ishikawa cells as the control culture. They \nunderwent an oxidative challenge with a low concentration of hydrogen peroxide (H2O2) to assess the limitations of pure NAC therapy. \nAccording to the findings, ectopic 12Z tissue is prone to redox-induced stress; thus, its total intracellular glutathione content decreased \nby 72% under acute oxidative conditions. When used as a molecular modulator, NAC hindered lipid peroxidation and reduced \nmalondialdehyde (MDA) levels, which had increased threefold, back to baseline. Additionally, cytoplasmic proteins were resist ant to \noxidation due to NAC intervention; hence, there was no protein carbonylation in the test group, whereas there was a fourfold increase \nin protein carbonyl content. On the other hand, NAC could not reverse oxidative DNA fragmentation and genomic damage. Such a \nlimitation implies that iron -dependent DNA damage caused by endometrial hemorrhage cannot be targeted by a conventional radical \nscavenger such as NAC and that it occurs through alternative biochemical pathways.  \nAs for these models, although tissue viability is preserved, they can only be considered complete once metabolic manipulation s \nbeyond antioxidant monotherapy are undertaken. From the methodological point of view, major limitations should be considered.  For \nexample, in vitro  testing uses immortalized cell lines rather than primary human tissues, which cannot imitate all aspects of the \nphysiological processes occurring in living endometriotic tissue in vivo. Another limitation includes the use of cancerous Ishikawa cells \nto model oxidative conditions. Finally, it should be pointed out that iron -driven biochemical reactions resulting from erythrocyte \nhemolysis in human endometriomas are not accounted for in this traditional model (Coelho et al., 2026). \n \n\n \nREVIEW | OPEN ACCESS   \n \nMedical Science 30, e112ms3921 (2026)                                                                                                                                                               6 of 11 \nNAC in Multicomponent Supplementation \nWhile the individual effects of NAC are the primary topic of the review at hand, the complexity of endometriosis is reflected  by studies \nexploring multicomponent antioxidant supplementation. Research done with mouse models and endometriotic endothelial cells \ndemonstrates the ability of the three -component preparation containing NAC, alpha -lipoic acid, and bromelain to function as a \nmolecular modulator influencing the activity of endometriotic cells in specific ways. Together, this mixture brings about an increase in \nprogrammed cell death through caspase-3 and -7 activation and the downregulation of inflammatory factors such as VCAM-1 in lesion-\nderived endometriotic cells, without affecting normal myometrial/uterine cells. \n Clinical trials confirm these results with a decrease in cyst size and fewer cysts seen in the treated patients. Nonetheless,  this \nconclusion is based on the impact of the entire multicomponent formula rather than that of NAC only. There are some limitations of the \nin vivo  study to be noted here. For one, SCID mice were used for experiments, which means that their adaptive immune system is \ncompromised and does not fully represent the interaction between inflammation and other factors that are present in human \nendometriosis. In addition, a 21 -day-long intervention period cannot serve as an approximation for the multiyear -long development of \nthe disease, which is why cyst prevention cannot be confirmed (Agostinis et al., 2015).  \nIn the case of a multicenter clinical study conducted on the basis of the LEAP trial, a cohort of 346 female patients with \nendometriosis-related pelvic pain was investigated, where the subset included 45 women interested in pregnancy and not taking any \nhormonal medications. During a six -month follow-up protocol, the analysis showed decreased levels of pain scores according to VAS \n(6.66 ±1.81 to 3.14 ±2.22; P < 0.001). The study also showed significant changes associated with a decrease in the number of patients \nhaving high pain index values (from 40.2% at baseline to 3.6% at study conclusion; P < 0.001). In addition, the frequency of \nconsumption of standard analgesics was reduced, as the need for rescue NSAID became lower (86.4% to 37.4%; P < 0,001). From the \nstandpoint of methodology, as applicable for this review, it should be highlighted that the LEAP trial did not involve only t he NAC \nmedication as a monotherapy. Instead, participants received the mixture containing the NAC dose of 600 mg per day with 200 mg  of \nalpha-lipoic acid (LA), 25 mg of bromelain (Br), and 10 mg of zinc. Even though the data about 27 cases of spontaneous pregnancies \nshows potential for fertility enhancement in combination with pain control, the design of the experiment does not allow us to  prove \nany therapeutic effects of NAC specifically (Lete et al., 2018).  \nOther research focused on evaluating the synergism between NAC and natural polyphenolic agents (curcumin and quercetin). In a  \ntwofold approach, scientists used both the in vitro model based on endometrial cell cultures and the in vivo model involving 33 female \nsubjects diagnosed with endometriosis. Treatment with antioxidants in the combined form during 60 days contributed toward \nimproved pain indices, including reduction in dysmenorrhea (Numeric Rating Scale NRS 6.1 to 2.8; P < 0.01), chronic pelvic pain (NRS \n5.7 to 2.1; P < 0.01), and dyspareunia (NRS 5.3 to 2.5; P < 0.01) and less consumption of NSAIDs. However, the use of the mixture still \nhinders the isolation of the impact of NAC treatment. Moreover, the small sample size limits further generalization due to li mited \ninformation on recurrence over several months (Fadin et al., 2020). Overall, these experiments confound existing evidence bec ause \nNAC cannot be identified as the factor responsible for the beneficial effects. \n \nFollicular Redox Modulation \nIn addition to modulating redox activity in endometriotic tissue, more comprehensive molecular effects have been studied in \nreproductive tissues. As has been shown, NAC promotes the nuclear translocation of nuclear factor erythroid 2 -related factor 2 (Nrf2), \nthereby triggering the transcription of several antioxidant enzymes in mouse oocytes (Fan et al., 2022). NAC was used to asse ss its \neffects on embryonic development and meiotic spindle integrity in oocytes from cows incubated with follicular fluid from patients with \nmild endometriosis characterized by increased oxidative stress (Giorgi et al., 2016; 2021). Nevertheless, these data warrant detailed \nconsideration, as oxidative stress is likely a downstream effect of the main pathogenesis of endometriosis (hormonal). The ex ternal \nvalidity of these studies is poor; therefore, they can be interpreted only as explorations, as there is still insufficient ev idence for clinical \nuse. As mentioned above, NAC is considered as an intervention for improving oocyte quality. Therefore, a double -blind RCT of 25 \ninfertile women with stage III/IV endometriosis was conducted to explore this issue further. In the absence of statistical si gnificance, \nthese clinical results must be interpreted as preliminary given the small sample size. The study showed an improvement in Tot al \nAntioxidant Capacity (TAC) upon administration of 1200 mg/day of NAC for six weeks ( P = 0.031). Moreover, cellular analysis of GCs \nconfirmed a defensive mechanism through downregulation of BAX and CASP-3, responsible for apoptosis, and upregulation of BCL2 \n(P < 0.05). There was also a lower percentage of defunct oocytes (4.9%) versus the placebo group (6.1%). Although this study pro vides \n\n \nREVIEW | OPEN ACCESS   \n \nMedical Science 30, e112ms3921 (2026)                                                                                                                                                               7 of 11 \nan approach to exploring the redox-mediated oocyte protection mechanism, there is insufficient evidence for this biological shift, as the \nsample size of 25 participants is too small (Heshmati et al., 2026). \n \n4. DISCUSSION \nThe literature on NAC in endometriosis varies, ranging from experimental laboratory data to clinical research. The research o n in vitro \nmodels has reported interesting NAC’s coaction with IFN -γ, involving stress -related organelle signaling (Karakoç et al., 2025). \nHowever, experimental works have certain limitations. More precisely, most experiments use immortalized 12Z and HESC cell lines, \ntogether with cancer -like control cells that cannot imitate complicated, inflammatory conditions typical of the pelvic area and do not \ninvolve iron metabolism pathways (Karakoç et al., 2025; Coelho et al., 2026). This limits their external validity and ability  to replicate \nchronic and progressive features inherent to human endometriosis.  \nPreclinical animal studies involving rodents have shown both lesion regression and decreased cytokine levels. Although the re sults \nmay seem positive, they cannot be generalized to clinical benefits due to the use of surgically induced implants, an acute fo rm of \ndamage rather than a progressive inflammation that defines endometriosis. These studies also use a small subgroup, a very sho rt time \nof drug administration, and no specific human clinical outcomes, making it difficult to infer the possible durable effectiven ess or safety \nof the therapy (Pittaluga et al., 2010; Onalan et al., 2014; Lu et al., 2020; Agostinis et al., 2015).  \nClinical evidence gathered via observational studies, as well as prospective trials involving single -arm analyses and multicenter \nstudies, faces additional challenges because NAC is often included in multi -component drugs containing LA, Br, and zinc. Multiple \nsubstances make it impossible to identify the actual effects of NAC, hence limiting the possibility of attributing beneficial  effects \nobserved in patients to it (Agostinis  et al., 2015; Lete et al., 2018; Fadin et al., 2020). Moreover, the research on this topic features many \nlimitations in methodology, like the use of non -randomized study designs, a lack of placebo controls, insufficient numbers of \nparticipants, and very limited follow -ups, which do not allow the assessment of lesion regression, alleviation of pain or any other \nreported change in the long term (Porpora et al., 2013; Anastasi et al., 2023).  \nOverall, the current state of knowledge, ranging from cellular processes to clinical findings in humans, remains highly explo ratory. \nThe reliance on artificially created cells, experimentally operated animals, and unclear multi -component compositions in clinical \nsettings precludes establishing NAC as the standard. To make the comparison more transparent, a table 1 has been provided. In  \naddition, the exploratory nature of the findings is evident in reproductive research. While animal experiments suggest benefi ts of NAC \non egg quality, human tissue samples were not used in this case (Fan et al., 2022; Giorgi et al., 2016; 2021). Pilot human trials in this area \nhave suffered from low power and a lack of clear results (Heshmati et al. 2026).  \n \nTable 1. Overview of preclinical and clinical studies investigating NAC in endometriosis. \nAuthor  Study design Sample size Intervention Main Outcomes Principal Limitations \nPittaluga et al., \n2010 \n \nExperimental \nmurine study  n = 40 mice \nNAC oral \nadministration \nvs. untreated \ncontrols \n60% reduction in lesion \nmass; Ki-67 decrease (52% \nto 23%); repositioning of \njunctional E-cadherin; \ndownregulation of Cox2 \nand MMP-9. \nAnimal model: limited \ntranslational relevance \nto human tissue. \nPorpora et al., \n2013 \nSingle-center \nobservational \ncohort \nn = 92 \nwomen (47 \nNAC-\ntreated; and \n45 control \ngroup) \nNAC oral “pulse \ntherapy” \n(1.8 g/day, \n3 days/week) for \n3 months \nMean cyst reduction of \n1.5 mm (vs 6.6 mm \nincrease in controls \nP = 0.001); relief in \ndysmenorrhea \n(55%, P = 0.001), \ndyspareunia \n(50%, P = 0.027), chronic \npelvic pain \n(59%, P = 0.015). \nNon-randomized \ndesign; single-center \ndesign: limited \nexternal validity; small \ncohort; short follow-up \nperiod; lack of placebo \ncontrol. \nAnastasi et al., Prospective n = 120 NAC oral “pulse Reduction in VAS score: Non-randomized, \n\n \nREVIEW | OPEN ACCESS   \n \nMedical Science 30, e112ms3921 (2026)                                                                                                                                                               8 of 11 \n2023 single-arm \ncohort \nwomen therapy” \n(1.8 g/day, \n3 days/week) for \n3 months \ndysmenorrhea (6.9 to 4.8; \nP < 0.0001), chronic pelvic \npain (7.2 to 5.7; P < 0.001); \ndecrease in cyst size (36.5 \nto 33.0 mm, P < 0.001); \nreported spontaneous \npregnancies. \nsingle-arm design: \nabsence of control \ngroup; small cohort; \nbrief follow-up period; \nincoherence in \nmetabolic shifts (BMI); \nbehavioral \nconfounding of \nreproductive data. \nKarakoç et al., \n2025 \nIn vitro \nexperimental \nstudy \nHuman cell \nlines (12Z/ \nHESC) \nAddition to \nculture medium \n(NAC combined \nwith IFN-) \nSynergistic induction of \nmitochondrial \ndysfunction and ER stress \nvia p-IRE1-; suppression \nof energy pathways \ncausing cellular \nstarvation. \nModeling gap using \nimmortalized cell lines: \nexaggerated metabolic \nshifts; ineffective \nagainst IL-6 or TNF- \ndriven proliferation.  \nOnalan et al., \n2014 \nExperimental \nin vivo animal \nstudy \nn = 40 female \nrats \nNAC vs. \nLeuprolide \nacetate and \namifostine \nMacroscopic regression of \nendometriotic implant \nsurface area \n(61.2±57.9 mm2 to \n30.5±21.9 mm2; P = 0.043); \ndecrease in TNF- \nsystemic (41.7±9.9 pg/ml \nto 17.25±10.1 pg/ml; \nP = 0.01) and local \nperitoneal fluid \n(37.5± 15.3 pg/ml to \n19.2±13.1 pg/ml; P =0.06). \nSurgically induced \nmodel does not \nreplicate spontaneous \nhuman disease \npathogenesis; acute 3-\nweek treatment limits \nlong-term relevance; \nlacks human clinical \nendpoints. \nLu et al., 2020 \nExperimental \nin vivo animal \nstudy \nn = 50 female \nrats \nNAC (21 days) \nvs. Catalase and \nControl \nReduced Local ROS \nlevels; downregulated \nautophagy markers (LC3 \nand Beclin-1) in ectopic \nlesions. \nSurgically induced \nanimal model does not \nmimic human \npathogenesis; small \nsample size per \nsubgroup. \nCoelho et al., \n2026 \nIn vitro 2D and \n3D spheroid \nexperimental \nstudy  \nHuman cell \nlines (12Z vs. \nIshikawa) \nPretreatment \nwith isolated \nNAC (5mM in \n2D / 1.25mM in \n3D) prior to \ncontrolled H2O2 \noxidative \nchallenge \nNAC restored cell \nviability and prevented \nlipid peroxidation and \nprotein carbonylation; 3D \nmodeling captured a 72% \ndepletion of the total \nglutathione pool; NAC \nfailed to mitigate \noxidative DNA \nfragmentation. \nLow external validity: \nin vitro architecture \nusing immortalized \ncells lacking \nmulticellular and \ninflammatory \ncomplexity of in vivo \nlesions; \nadenocarcinoma origin \nof the comparator line \nintroduces cancer-\nspecific redox \nadaptations; lacks iron-\ndriven pathways. \n\n \nREVIEW | OPEN ACCESS   \n \nMedical Science 30, e112ms3921 (2026)                                                                                                                                                               9 of 11 \nAgostinis et al., \n2015 \nExperimental \nin vitro / in vivo \nmurine study \nn = 16 SCID \nmice and \nhuman \nendothelial \ncell lines \n(EECs/UtME\nCs) \nOral \nadministration \nof combined \nmixture (NAC \n250 m + LA \n125 mg + Br \n12.5 mg / day) \nvs. untreated \ncontrols \nLower number and \nsmaller size of cysts in \nvivo; synergistic \ndownregulation of \nVCAM-1 expression in \nEECs; selective induction \nof apoptosis via caspases \n3 and 7 activation. \nLow external validity: \npreclinical animal \nmodel using SCID \nmice lacking functional \nadaptive immunity; \nextremely brief 21-day \nintervention \ntimeframe; therapeutic \nsuccess depends on \nmulti-ingredient \nsynergy. \nLete et al., 2018 \n \nMulticenter, \nopen-label, \nnon-\ncomparative \nclinical trial \nn = 346 \nwomen  \nOral intake of a \ncombination \ntablet containing \n600 mg NAC, \n200 mg LA, \n25 mg Br, 10 mg \nZinc/day for 6 \nmonths \nSignificant drop in mean \nVAS scores (6.66 to 3.14; \nP < 0.001); a reduction in \nthe proportion of patients \nsuffering from severe \npain (40.2% to 3.6%; \nP < 0.001); reduction in \nrescue NSAIDs reliance \nfrom 86.4% to 37.4% \n(P < 0.001); 27 \nspontaneous pregnancies. \nOpen-label, non-\ncomparative trial; \narchitecture lacking \nplacebo control arm; \nlow specificity: fixed \nmulticomponent \nformulation makes it \nimpossible to isolate or \nverify the therapeutic \neffect of the NAC \nmodule. \nFadin et al., \n2020 \n \nExperimental \nin vitro and in \nvivo medical \ntrial \nIn vitro (-\nestradiol-\ninduced \nendometrial \ncells) and \nn = 33 \nwomen \nNAC+ Tumeric + \nQuercetin for 60 \ndays \nIn vitro: Downregulated \npro-inflammatory \ncytokines (IL-6, TNF-) \nand induced apoptosis. \nIn vivo: Reduced \ndysmenorrhea (NRS \n6.1 to 2.8; P < 0.01), \nchronic pelvic pain (NRS \n5.7 to2.1; P < 0.01) and \ndyspareunia (NRS \n5.3 to 2.5; P < 0.01) as well \nas a decrease in NSAID \nreliance. \nSmall sample size; \nshort follow-up \nduration; lack of a \nrandomized placebo \ncontrol group; low \nspecificity: the \nisolation of NAC’s \neffect is not possible \n \n5. CONCLUSION \nDespite the present research on NAC in the context of endometriosis, the existing translational gap cannot be ignored, with a  simple \nexperimentation design being used and clinical research being structurally invalid. It uses immortalized cells in vitro as well as animals \nthat underwent surgery to create similar conditions. Most importantly, the existing data from clinical experiments are compro mised by \nthe simultaneous use of several components of treatment. Observational studies, in addition, suffer from relatively small sample sizes, a \nlack of randomization, and inadequate follow -up. The placebo effect can easily influence the results of such studies, leading to high \nbias. The only solution here would be to move on to conducting RCTs in which NAC is used as the sole intervention. \n \nAcknowledgments \nThere are no acknowledgments to disclose. \n \n \n\n \nREVIEW | OPEN ACCESS   \n \nMedical Science 30, e112ms3921 (2026)                                                                                                                                                               10 of 11 \nAuthors’ Contributions \nConceptualization: Magdalena Rakuś \nMethodology: Magdalena Rakuś, Krzysztof Łukasz, Jakub Marzec, Michał Nowakowski, Aleksandra Musioł, Paweł Gwałt \nResources: Magdalena Rakuś, Krzysztof Łukasz, Jakub Marzec, Michał Nowakowski, Aleksandra Musioł, Paweł Gwałt \nInvestigation: Magdalena Rakuś, Krzysztof Łukasz, Jakub Marzec, Michał Nowakowski, Aleksandra Musioł, Paweł Gwałt \nWriting-rough preparation: Magdalena Rakuś, Krzysztof Łukasz, Jakub Marzec, Michał Nowakowski, Aleksandra Musioł, Paweł \nGwałt \nWriting-editing: Magdalena Rakuś, Krzysztof Łukasz, Jakub Marzec, Michał Nowakowski, Aleksandra Musioł, Paweł Gwałt \nSupervision: Magdalena Rakuś \nAll authors have read and agreed to the published version of the manuscript.   \n \nInformed consent \nNot applicable. \n \nEthical approval \nNot applicable. This article does not contain any studies with human participants or animals performed by any of the authors. \n \nFunding \nThis research did not receive any external funding like specific grant from funding agencies in the public, commercial, or nonprofit \nsectors. \n \nConflict of interest \nThe authors declare that they have no conflicts of interest, competing financial interests or personal relationships that could have \ninfluenced the work reported in this paper. \n \nData and materials availability \nAll data associated with this study will be available based on the reasonable request to corresponding author. \n \nREFERENCES \n1. Agostinis C, Zorzet S, De Leo R, Zauli G, De Seta F, Bulla R. \nThe combination of N -acetyl cysteine, alpha -lipoic acid, and \nbromelain shows high anti -inflammatory properties in novel \nin vivo and in vitro models of endometriosis. Mediators \nInflamm 2015;2015:918089. doi: 10.1155/2015/918089. \n2. Anastasi E, Scaramuzzino S, Viscardi MF, Viggiani V, Piccioni \nMG, Cacciamani L, Merlino L, Angeloni A, Muzii L, Porpora \nMG. Efficacy of N -Acetylcysteine on Endometriosis -Related \nPain, Size Reduction of Ovarian Endometriomas, and Fertility \nOutcomes. Int J Environ Res Public Health 2023;20(6):4686. \ndoi: 10.3390/ijerph20064686. \n3. As-Sanie S, Mackenzie SC, Morrison L, Schrepf A, Zondervan \nKT, Horne AW, Missmer SA. Endometriosis: A Review. \nJAMA 2025;334(1):64-78. doi: 10.1001/jama.2025.2975. \n4. Becker CM, Bokor A, Heikinheimo O, Horne A, Jansen F, \nKiesel L, King K, Kvaskoff M, Nap A, Petersen K, Saridogan \nE, Tomassetti C, van Hanegem N, Vulliemoz N, Vermeulen N; \nESHRE Endometriosis Guideline Group. ESHRE guideline: \nendometriosis. Hum Reprod Open 2022;2022(2):hoac009. doi: \n10.1093/hropen/hoac009. \n5. Clower L, Fleshman T, Geldenhuys WJ, Santanam N. \nTargeting Oxidative Stress Involved in Endometriosis and Its \nPain. Biomolecules 2022;12(8):1055. doi: 10.3390/biom12081  \n055. \n6. Coelho JA, Gomes KS, Cerchiaro  G. Differential Antioxidant \nCapacities of Human Endometriotic and Endometrial Cell \nModels Under H2O2 Exposure. Int J Mol Sci 2026;27(9):4131. \ndoi: 10.3390/ijms27094131. \n7. Facchin F, Vercellini P, Somigliana E. The impact of \nendometriosis on educational and professional pathways: a \ncross-sectional online study. BMC Psychol 2026;14(1):303. doi: \n10.1186/s40359-026-04112-5. \n8. Fadin M, Nicoletti MC, Pellizzato M, Accardi M, Baietti MG, \nFratter A. Effectiveness of the integration of quercetin, \nturmeric, and N -acetylcysteine in reducing inflammation and \npain associated with endometriosis. In -vitro and in -vivo \n\n \nREVIEW | OPEN ACCESS   \n \nMedical Science 30, e112ms3921 (2026)                                                                                                                                                               11 of 11 \nstudies. Minerva Ginecol 2020;72(5):285 -291. doi: 10.23736/S00 \n26-4784.20.04615-8. \n9. Fan L, Guan F, Ma Y, Zhang Y, Li L, Sun Y, Cao C, Du H, He \nM. N -Acetylcysteine improves oocyte quality through \nmodulating the Nrf2 signaling pathway to ameliorate \noxidative stress caused by repeated controlled ovarian \nhyperstimulation. Reprod  Fertil Dev 2022;34(10):736 -750. doi: \n10.1071/RD22020. \n10. Giorgi VS, Da Broi MG, Paz CC, Ferriani RA, Navarro PA. N-\nAcetyl-Cysteine and l -Carnitine Prevent Meiotic Oocyte \nDamage Induced by Follicular Fluid From Infertile Women \nWith Mild Endometriosis. Reprod Sci 2016;23(3):342 -51. doi: \n10.1177/1933719115602772. \n11. Giorgi VSI, Ferriani RA, Navarro PA. Follicular Fluid from \nInfertile Women with Mild Endometriosis Impairs In Vitro \nBovine Embryo Development: Potential Role of Oxidative \nStress. Rev Bras Ginecol  Obstet 2021;43(2):119 -125. doi: \n10.1055/s-0040-1718443. \n12. Heshmati ZS, Amiri -Yekta A, Khosravifar M, Akbarian F, \nMoini A, Eftekhari -Yazdi P, Hafezi M, Afsharian P. \nAdministration of N-acetylcysteine influence the expression of \napoptotic genes in the granulosa cells of infertile women \ndiagnosed with endometriosis. Sci Rep 2026;16(1):7961. doi: \n10.1038/s41598-025-34202-0. \n13. Karakoç E, Halaçlı SO, Hanelçi RH, Ayhan S, Eylem CC, \nNemutlu E, Atilla P. N -acetylcysteine stimulates organelle \nmalfunction in endometriotic cells via IFN -gamma signaling. \nSci Rep 2025;15(1):15120. doi: 10.1038/s41598-025-00195-z. \n14. Lete I, Mendoza N, de la Viuda E, Carmona F. Effectiveness of \nan antioxidant preparation with N -acetyl cysteine, alpha \nlipoic acid and bromelain in the treatment of endometriosis -\nassociated pelvic pain: LEAP study. Eur J Obstet Gynecol \nReprod Biol 2018;228:221 -224. doi: 10.1016/j.ejogrb.2018.07.00  \n2. \n15. Li Y, Gong Y, Jiang H, Ji M. Impact of endometriotic \ncystectomy on ovarian reserve function and ovulation \ninduction outcomes in women with endometriosis \nundergoing assisted reproductive technology. Front \nEndocrinol (Lausanne) 2026;16:1687765. doi: 10.3389/fendo.  \n2025.1687765. Erratum in: Front Endocrinol (Lausanne) 2026;  \n17:1806799. doi: 10.3389/fendo.2026.1806799. \n16. Lu H, Hu H, Yang Y, Li S. The inhibition of reactive oxygen \nspecies (ROS) by antioxidants inhibits the release of an \nautophagy marker in ectopic endometrial cells. Taiwan J \nObstet Gynecol 2020;59(2):256 -261. doi: 10.1016/j.tjog.2020.01.  \n014. \n17. Onalan G, Gulumser C, Mulayim B, Dagdeviren A, \nZeyneloglu H. Effects of amifostine on endometriosis, \ncomparison with N -acetyl cysteine, and leuprolide as a new \ntreatment alternative: a randomized controlled trial. Arch \nGynecol Obstet 2014;289(1):193 -200. doi: 10.1007/s00404 -013-\n2963-0. \n18. Pittaluga E, Costa G, Krasnowska E, Brunelli R, Lundeberg T, \nPorpora MG, Santucci D, Parasassi T. More than antioxidant: \nN-acetyl-L-cysteine in a murine model of endometriosis. Fertil \nSteril 2010;94(7):2905-8. doi: 10.1016/j.fertnstert.2010.06.038. \n19. Porpora MG, Brunelli R, Costa G, Imperiale L, Krasnowska \nEK, Lundeberg T, Nofroni I, Piccioni MG, Pittaluga E, Ticino \nA, Parasassi  T. A promise in the treatment of endometriosis: \nan observational cohort study on ovarian endometrioma \nreduction by N -acetylcysteine. Evid Based Complement \nAlternat Med 2013;2013:240702. doi: 10.1155/2013/240702. \n20. Taylor HS, Kotlyar AM, Flores VA. Endometriosis is a chronic \nsystemic disease: clinical challenges and novel innovations. \nLancet 2021;397(10276):839 -852. doi: 10.1016/S0140 -6736(21)00 \n389-5. \n21. Tomassetti C, Johnson NP, Petrozza J, Abrao MS, Einarsson JI, \nHorne AW, Lee TTM, Missmer  S, Vermeulen N, Zondervan \nKT, Grimbizis G, De Wilde RL. An international terminology \nfor endometriosis, 2021. Hum Reprod Open  2021(4):hoab029. \ndoi: 10.1093/hropen/hoab029. \n22. Veth VB, Keukens A, Reijs A, Bongers MY, Mijatovic V, \nCoppus SFPJ, Maas JWM. Recurrence after surgery for \nendometrioma: a systematic review and meta -analyses. Fertil \nSteril 2024;122(6):1079-1093. doi: 10.1016/j.fertnstert.2024.07.03  \n3. \n23. Zondervan KT, Becker CM, Missmer  SA. Endometriosis. N \nEngl J Med 2020;382(13):1244 -1256. doi: 10.1056/NEJMra1810  \n764.","source_license":"CC0","license_restricted":false}