The peritoneal environment in endometriosis

The local environment of peritoneal fluid (PF) surrounding the endometriotic implant is immunologically dynamic and links the reproductive and immune systems. Peritoneal fluid contains a variety of free floating cells, including macrophages, mesothelial cells, lymphocytes, eosinophils and mast cells. Macrophages are attracted to the peritoneal environment more abundantly than any other cell type. These scavengers promote cellular growth and viability through secretion of growth factors and cytokines. It is now becoming evident that cytokines play an important role in reproduction at various levels, including gamete function, fertilization and embryo development, implantation and postimplantation survival of the conceptus. Peritoneal fluid has been shown to affect negatively ovum capture by the fimbria, sperm survival, spermatozoon-oocyte interaction and embryonic development. We have recently identified the presence of two pro-inflammatory chemoattractant cytokines for monocyte/macrophages (MCP-1) and for granulocytes (interleukin-8, IL-8) in the PF. Concentrations of both IL-8 and MCP-1 are not only elevated in PF of women with endometriosis compared to those without endometriosis, but they are related to the severity of the disease. Over the past 70 years, at least a dozen theories have been proposed to explain the histogenesis and aetiology of endometriosis. It appears that the aetiology is multifactorial, and today a composite theory of retrograde menstruation with implantation of endometrial fragments in conjunction with peritoneal factors to stimulate cell growth is the most widely accepted explanation for peritoneal endometriosis.     

Abdominopelvic washings in gynecologic pathology: A comprehensive review

Abdominopelvic washings (APW) performed during gynecologic surgeries have become a common specimen evaluated by cytopathologists. Their role in staging of female genital tract tumors has changed significantly since they were first described, and continue to evolve. The ability of these washings to detect microscopic disease, even in the absence of gross disease, warrants the critical role that these washings play in the staging of certain female gynecologic tract tumors, allowing for optimal staging and subsequent treatment of the patient. Irrespective of the underlying pathology, the gamut of cytomorphologic findings that may be observed in APW is extensive, and ranges from benign lesions that may act as mimickers of malignancy, to both common and rare malignancies. This review discusses the changing role of APW in the staging of gynecologic tumors, and highlights the salient cytomorphologic features of these lesions, with emphasis in their correct identification, including cautionary notes to avoid over or misinterpretation. Diagn. Cytopathol. 2016;44:1039–1057. © 2016 Wiley Periodicals, Inc.     

Single-cell Raman trapping analysis revealed immunometabolism changes in peritoneal fluid in endometriosis

In endometriosis, an aberrant immune response in the peritoneal environment is evident, but the underlying mechanism remains unclear. In recent years, some emerging data support an important role for the changes in intracellular metabolic pathways of immune cells in controlling their function. In this study, we aim to investigate the phenotypic and immunometabolism profiling of peritoneal fluid cells in endometriosis patients. By flow cytometry, our results show phenotypic profiling of peritoneal fluid cells with higher percentages of CD45⁺, CD3⁺, CD3⁺CD8⁺, CD3⁺CD56^+, and CD14⁺CD68⁺ cells and the ratio of M2 to M1 macrophages but less CD14^?CD86⁺ dendritic cells in endometriosis when compared with control. Label-free single-cell Raman trapping analysis shows intracellular changes in decreased collagen, proteins and lipids levels in CD45⁺ immune cells in endometriosis. In the supernatant of peritoneal fluid from endometriosis patients, Raman results reveal extracellular decreased protein and carbohydrate levels but increased lipid and fatty acid levels. Especially, Raman bands indicate both intracellular and extracellular levels of cholesterol and carotenoids decrease in endometriosis patients when compared with controls. This study provides immunometabolism features of the specific microenvironment in the peritoneal cavity and identifies some biological molecules associated with immune dysfunction in endometriosis, which may offer new clues for understanding disease pathology and therapeutic targets.     

Erythropoietin concentrations are elevated in the peritoneal fluid of women with endometriosis

Erythropoietin (Epo) is an important regulator of erythropoiesis and stimulates the proliferation of early erythroid precursors as well as the differentiation of late erythroid precursors of the erythroid lineage. However, recent studies have indicated that Epo also has angiogenic properties and plays an important role in the oestrogen-dependent cyclical angiogenesis within the mouse uterus. It was therefore postulated that Epo may be an important angiogenic factor in endometriosis. In order to address this hypothesis the concentration of Epo in peritoneal fluid (PF) was determined in patients with or without endometriosis. PF was collected from patients with endometriosis (n = 42) or without endometriosis (n = 18). Detectable concentrations of Epo were found in all PF samples analysed. The concentration of Epo in PF from patients with endometriosis was significantly higher than that in the control group (13.1 +/- 1.2 mIU/ml versus 7.2 +/- 0.7 mIU/ml, mean +/- SE respectively, P < 0.01). Furthermore, in patients with endometriosis the Epo concentrations in PF from patients with stage I disease (n = 17, 16.6 +/- 3.0 mIU/ml) were significantly higher than those with stage II (n = 8, 10.7 +/- 1.2 mIU/ml, P < 0.03), III (n = 13, 8.4 +/- 1.0 mIU/ml, P < 0.01), IV disease (n = 7, 7.5 +/- 1.0 mIU/ml, P < 0.01). These data suggest that Epo may play a role in the pathogenesis of endometriosis particularly in the initiation of the disease.     

Diagnostic pitfalls of peritoneal washing cytology and the role of cell blocks in their diagnosis

Mesothelial cell hyperplasia, collagen balls, endometriosis, and endosalpingiosis are diagnostic pitfalls on peritoneal washing cytology in women who present with gynecologic lesions. Over an 8-month period, the peritoneal washings from 10 patients undergoing gynecologic surgery for presumed malignancy showed unusual cytologic findings, several of which posed diagnostic difficulties. The washings from four patients with ovarian carcinomas were cellular and contained clusters and strips of cells with cytologic atypia mimicking malignancy. Confirmation of their benign mesothelial origin was confirmed on immunohistochemistry utilizing cell block preparations. In two cases of endometrial endometrioid carcinoma, the washings contained several clusters of cells surrounding and/or admixed with a globular substance. Due to their similarity to endometrial cells, immunohistochemistry was performed on cell block preparations. The cells were positive for cytokeratin and negative for carcinoembryonic antigen and B72.3, confirming their mesothelial origin. In one case, clinically presumed to be a malignant mass, the washings contained tight clusters of cells with mild cytologic atypia admixed with hemosiderin-laden macrophages. In conjunction with the cell block findings, a diagnosis of endometriosis was made. Extensive endometriosis was found on the surgically resected specimen. In two cases, strips of ciliated epithelial cells resembling tubal epithelium were present on the cytologic and cell block preparations, consistent with endosalpingiosis. The peritoneal washings in one case contained several clusters and balls of atypical cells surrounding microcalcifications on cell block preparation. Since calcification within groups of cells in peritoneal washings always raised the possibility of malignancy, a serous carcinoma of the ovary, particularly of borderline malignancy, would have to be excluded. Fortunately, the resected specimen was free of tumor and showed calcified endosalpingiosis on the ovarian surface. Preparation of cell blocks from peritoneal washings is of value in the work-up and management of patients who present with cytologic mimickers of malignancy on fluid cytology.     

CA 125 in peritoneal fluid from patients with endometriosis.

This study was performed to evaluate CA 125 in peritoneal fluid as an indicator of endometriosis. Peritoneal fluid from patients with mostly minimal and mild endometriosis (n = 43) and normal controls (n = 17) was collected at laparoscopy or laparotomy. The median concentration of CA 125 in peritoneal fluid did not differ significantly between patients and controls (79 IU/ml versus 76 IU/ml). In patients with endometriosis, a significantly increasing concentration of CA 125 in peritoneal fluid was seen from the early follicular to the late luteal phase; a similar change was not observed in the controls. In 14 patients, peritoneal fluid was sampled again after treatment with danazol and a significant reduction in median CA 125 concentration (76.5 IU/ml versus 57 IU/ml), peritoneal fluid volume (17.5 ml versus 10.5 ml) as well as reduced endometriosis scores (4 versus 2) were found. In controls, the concentration of CA 125 was about 10 times higher in peritoneal fluid than in serum. As the peritoneal levels of CA 125 did not differ significantly between patients with endometriosis and controls and as the reduction seen after danazol treatment did not correlate with the decrease of endometriotic implants, it is concluded that the monitoring of CA 125 in peritoneal fluid will not be useful in the diagnosis or control of endometriosis.     

Hepatocyte growth factor concentrations are elevated in peritoneal fluid of women with endometriosis.

The concentrations of hepatocyte growth factor (HGF) in peritoneal fluid (PF) from women with endometriosis (n = 36) and without endometriosis (n = 40) were measured. All of the PF samples examined contained detectable concentrations of HGF. The HGF concentrations in PF from women with stage III/IV endometriosis (0.906 ng/ml, 0. 561-1.185; median, interquartile range) were significantly higher (P < 0.0001) than those from women without endometriosis (0.315 ng/ml, 0.251-0.472). The HGF concentrations from women with stage I/II endometriosis (0.417 ng/ml, 0.310-1.023) appeared to be intermediate. There were no apparent variations detected among the HGF concentrations in women in the follicular or luteal phases regardless of the presence of endometriosis. Interestingly, HGF concentrations in PF from women on gonadotrophin releasing hormone analogues, independent of the presence of endometriosis, were comparable with those from untreated women. Given the known mitogenic property of HGF in human endometrial cells, these results suggest that HGF might play a role in the progression of endometriosis.     

Inverse correlation between peritoneal fluid leptin concentrations and the extent of endometriosis

BACKGROUND: The role of leptin in reproductive processes has received increasing attention. Because leptin has intrinsic angiogenic properties, may be induced by inflammatory cytokines and induces matrix metalloproteinases, we examined peritoneal fluid (PF) leptin concentrations in women with endometriosis. METHODS: PF samples were collected from 60 women undergoing laparoscopy for endometriosis, and 18 controls undergoing tubal sterilization. Fifty of the women with endometriosis had received no prior hormonal treatment, while 10 with moderate- severe endometriosis were using GnRH agonists. RESULTS: Women with untreated endometriosis had significantly higher (mean +/- SD) PF leptin levels (34.9 +/- 7.9 ng/ml) than controls (17.9 +/- 4.1 ng/ml; P < 0.001). However, PF leptin levels were inversely correlated with the stage of disease (r = -0.62; P < 0.001). Nevertheless, women with stage III-IV endometriosis maintained significantly higher PF leptin levels (26.3 +/- 4.8 ng/ml; P < 0.001) than controls. Although PF leptin levels were significantly higher in the secretory versus proliferative phase of the menstrual cycle, they remained higher in both phases in women with untreated endometriosis. PF leptin levels in women on GnRH agonists were similar to controls. CONCLUSIONS: PF leptin levels are elevated in women with endometriosis, but inversely correlated with extent of disease. These findings suggest a potential role for leptin in the pathogenesis of peritoneal endometriosis.     

Endometriotic disease: the role of peritoneal fluid

Peritoneal fluid and the intraovarian milieu are a specific microenvironment. Peritoneal fluid originates mainly as an ovarian exudation product caused by increased vascular permeability, with cyclic variation in volume and steroid hormones which are always higher than in plasma. It contains large amounts of macrophages and their secretion products, and has a large exchange area with plasma through the peritoneum, which is highly permeable for small molecules. Diffusion becomes virtually zero for molecules with a molecular weight of >100000 Da. In women with the luteinized unruptured follicle (LUF) syndrome, concentrations of oestrogens and progesterone are much lower in the luteal phase. Endometriosis is associated with sterile low-grade inflammation, increased concentrations of activated macrophages and many of their secretions, such as cytokines, growth factors and angiogenic factors. Concentrations of CA-125 and of glycodelins are also increased, secreted locally by the endometrial cells. Natural killer (NK) cell function declines, possibly mediated by glycodelins or local intercellular adhesion molecule (ICAM) -1 shedding. The ovary is also a specific microenvironment, with steroid hormone concentrations 1000-fold higher in follicles than in plasma. Endometrial and superficially implanted cells are influenced by peritoneal fluid concentrations so that local environment, rather than inherent cellular differences could explain differences between superficial endometriosis and eutopic endometrium. Differences between superficial implants and endometriotic disease, deep infiltrating or cystic ovarian endometriosis, may thus arise via different endocrine environments. Superficial endometrial implants are regulated by peritoneal fluid factors, whereas deep endometriosis and cystic ovarian endometriosis are influenced by blood or ovarian factors. The endometriotic disease theory considers superficial endometriotic implants and their remodelling as a physiological process in most women, and concentrates on the causes of severe endometriosis such as differences in the eutopic endometrium from women with and without endometriosis (which may indicate hereditary differences), the invasiveness of some endometriotic cells in vitro, focal 'shielding' of endometriotic foci by adhesions, and inhibition of NK activity by ICAM-1 and glycodelins. Endometriotic disease is thus seen as a benign tumour. The type of cellular lesion, hereditary and immunological environments and local hormone concentrations in the ovary and in peritoneal fluid, will decide expression as cystic ovarian endometriosis, deep endometriosis or adenomyosis externa, and whether the latter is associated with adhesions.     

Embryotoxicity of peritoneal fluid in women with endometriosis. Its relation with cytokines and lymphocyte populations

BACKGROUND: The goals of the present work were to study the embryotoxic effects of peritoneal fluid (PF) in women with or without endometriosis, and to relate any embryotoxicity to the severity of endometriosis, infertility or achievement of pregnancy, cytokine concentrations and lymphocyte populations. METHODS: Sixty-six consecutive women of reproductive age, 54 with endometriosis (21 infertile) and 12 infertile without endometriosis, and another 12 fertile women as control group, were included in this study. They all underwent laparoscopy or laparotomy in the second half of the cycle, and PF was collected from the pouch of Douglas. The embryotoxicity of the PF was assessed by means of a mouse embryo assay, and expressed as the number of embryos that did not reach blastocyst stage. Cytokines and lymphocyte populations present in PF were also studied and correlated with embryotoxicity. RESULTS: PF embryotoxicity was increased in women with endometriosis, but there was little correlation with the severity of the disease. However, although a clear relationship to the presence of infertility was not found, embryotoxicity appeared to be lower in those infertile patients with endometriosis who later became pregnant. We found a significant increase in embryotoxicity in the presence of high cytokine concentrations, especially with interleukin-6, and less so with interleukin-8 (P < 0.05). No good correlation was observed with lymphocyte populations, but CD56 (NK) cells were significantly increased in the PF of women with endometriosis. In general, the correlations for embryotoxicity were better when PF was diluted at 20% (91.4 +/- 17 versus 68.1 +/- 31, P < 0.01). CONCLUSIONS: These results suggest that alteration in the production of cytokines in the PF, especially IL-6, besides contributing to the endometriosis and its evolution, probably increases embryotoxicity. However, no correlation was found between the latter and associated infertility.     

Concentration of adiponectin in peritoneal fluid is decreased in women with endometriosis

PROBLEM: Adiponectin is a novel adipocytokine of extreme importance for the metabolism. Recent studies have indicated that adiponectin suppresses inflammation, angiogenesis, and fibrosis, which are central pathogenic factors for endometriosis. We addressed the possibility that adiponectin is implicated in endometriosis. METHOD OF STUDY: We measured concentrations of adiponectin in peritoneal fluid (PF) of women with (n = 54) or without (n = 26) endometriosis using specific enzyme-linked immunosorbent assay. RESULTS: Adiponectin concentrations in PF of women with endometriosis were significantly lower than those of women without endometriosis. With respect to the stages of the disease, the concentrations of adiponectin in women with stage III/IV endometriosis were significantly lower compared to those in women without endometriosis and with stage I/II endometriosis. Body mass index were comparable among the groups. CONCLUSIONS: These findings imply that adiponectin may be an anti-endometriotic factor, possibly due to its anti-inflammatory, anti-angiogenic, and anti-fibrotic properties.     

Effects of peritoneal fluid from endometriosis patients on the release of vascular endothelial growth factor by neutrophils and monocytes

BACKGROUND: An increase in the level of the vascular endothelial growth factor (VEGF) production has been reported in the peritoneal fluid (PF) of endometriosis patients. This suggests that changes in the vascular permeability and angiogenesis play an important role in the pathophysiology of this disease. This study examined the effects of the PF obtained from endometriosis patients on the release of VEGF by neutrophils and monocytes. METHODS: Neutrophils and monocytes were obtained from young healthy volunteers and cultured with the PF obtained from either endometriosis patients (EPF) (n=18) or a control group (CPF) (n=4). A human monocyte/macrophage cell line, THP-1, was cultured with either 10% EPF or 10% CPF. The PF and culture supernatants were assayed for VEGF using ELISA. Real-time PCR and Western blotting were used to measure the VEGF mRNA and protein expression level, respectively. RESULTS: The VEGF levels were higher in the EPF than in the CPF (591+/-75 versus 185+/-31 pg/ml, P<0.05). However, the level of VEGF released by THP-1 cells in CPF and EPF was similar. The EPF induced the release of VEGF by neutrophils, but no VEGF was released by monocytes. The VEGF mRNA expression levels in the neutrophils were higher in the EPF, which was abrogated by cycloheximide, suggesting that the EPF induces the production of VEGF in neutrophils. Neutralizing antibodies against IL-8 and TNF-alpha did not completely prevent the EPF-induced release of VEGF by the neutrophils, even though these growth factors stimulated the release of VEGF by neutrophils. There was a positive correlation between the VEGF and IL-10 concentrations in the EPF (correlation coefficient=0.549, P=0.012, n=18), but the neutralizing antibody of IL-10 did not affect the release of VEGF by the EPF-treated neutrophils. CONCLUSION: The EPF induced the production and release of VEGF by neutrophils, suggesting that neutrophils may be a source of peritoneal VEGF. In addition, neutrophil-derived VEGF might be a marker for diagnosing endometriosis.     

Decreased amounts of antibodies to 22 and 18 kDa antigens in the peritoneal fluid of patients with endometriosis

Accumulated evidence implicates immunological alterations inendometriosis. The purpose of this study was to look for variationsin antibodies to distinct antigens in peritoneal fluid of womenwith and without endometriosis. Peritoneal fluid was aspiratedfrom 17 women undergoing laparoscopy for tubal ligation and37 patients complaining of symptoms of pain and/or infertility.Peritoneal fluid antibodies to a standard preparation of peritonealfluid antigens were detected by Western blot analysis usingperoxidase-labelled anti-human immunoglobulin G antibodies specificto the Fc region. Antibodies to distinct antigens were quantifiedby estimating the ratio of the relative optical density betweensamples and a standard amount of antibodies. Marked changeswere found in the antibody detection to two antigens havingapparent molecular weights of 22 and 18 kDa. The intensity ofthe antibody signal was significantly weaker in the peritonealfluid from endometriosis patients (0.36 ± 0.06 and 0.46± 0.06) compared with that in women without endometriosis(0.62 ± 0.08 and 0.75 ± 0.06). It was also weakerin patients without endometriosis presenting with infertility(036 ± 0.07 and 0.47 ± 0.08), but only the 18kDa antigen result was significant After adjusting for infertility,the P values for the 18 and 22 kDa bands were 0.03 and 0.28(not significant) respectively in the group of endometriosispatients. These changes were not related to the phase of themenstrual cycle. These data suggest an alteration in the immuneresponse to two distinct antigens in the peritoneal fluid fromwomen with endometriosis and infertility. Further evaluationof these two antigens and their antibodies would be of interestto help understand endometriosis and its associated infertility.     

Vascular endothelial growth factor (VEGF) concentrations are elevated in peritoneal fluid of women with endometriosis

Active endometriosis is characterized by hypervascularizationboth within and surrounding the implant; therefore the presenceof angiogenic factors in the peritoneal environment would beof great importance. Vascular endothelial growth factor (VEGF)is a potent angiogenic factor involved in both physiologicaland pathological angiogenesis. We sought to determine if VEGFwas present in the peritoneal fluid of women with and withoutendometriosis, and to establish if differences exist betweenthese groups. VEGF was present in all patients sampled. Thefluid from patients with endometriosis contained significantlygreater amounts of VEGF than controls. Cyclic variations inVEGF concentration were seen in fluid from patients with endometriosis,the VEGF concentration in proliferative phase being significantlyhigher than in the secretory phase. The concentration of VEGFin this fluid was also significantly higher than that foundin the proliferative and secretory phases of women without endometriosis.No cyclic variations in VEGF were seen in the control group.We suggest that elevated levels of VEGF in the peritoneal fluidof patients with endometriosis may be critical in the pathogenesisof endometriosis.     

Increased levels of interleukin-15 in the peritoneal fluid of women with endometriosis: inverse correlation with stage and depth of invasion

BACKGROUND: Interleukin (IL)-15 is a novel cytokine with immunoregulatory and angiogenic properties. We compared IL-15 levels in the peritoneal fluid (PF) of women with and without endometriosis. METHODS: PF samples were obtained from 55 women with endometriosis (23 with superficial peritoneal implants, 19 with deep endometriotic implants and 13 with ovarian endometriomas). Eighteen women with normal pelvic anatomy undergoing tubal sterilization served as controls. RESULTS: PF IL-15 concentrations were increased in women with endometriosis (2.7 +/- 0.5 pg/ml) versus controls (2.1 +/- 0.3 pg/ml; P < 0.001). However, IL-15 levels were higher in women with superficial peritoneal implants (2.9 +/- 0.5 pg/ml) than women with deep endometriotic implants (2.6 +/- 0.4 pg/ml; P = 0.01) or ovarian endometriomas (2.2 +/- 0.4 pg/ml; P < 0.001). IL-15 was also higher in women with deep implants than in those with endometriomas (P < 0.05). PF IL-15 correlated inversely with both depth of invasion (r = -0.52) and the stage of endometriosis (r = -0.42). PF IL-15 levels demonstrated little variation during the menstrual cycle, and did not discriminate between women with infertility or pelvic pain. CONCLUSION: PF IL-15 levels are increased in women with endometriosis. However, IL-15 levels are inversely correlated with the depth of invasion and disease stage, suggesting a possible role for this cytokine in the early pathogenesis of endometriosis.     

Endometriosis: Effect of peritoneal fluid from infertile women with endometriosis on ionophore-stimulated acrosome loss

The effect of peritoneal fluid (PF) from endometriosis patientswas studied in spontaneous and stimulus-induced (Ca-ionophore;A23187) acrosome reactions. PF samples were obtained from 21infertile women with endometriosis and five normal women (controls).Sperm acrosomes were examined by staining with Pisum sativumagglutinin labelled with fluorescein isothiocyanate. The incidenceof spontaneous acrosome reaction after 1 and 6 h of incubation(6.7 ± 1.6 and 6.9 ± 1.4 respectively) was significantly(P < 0.001) lower when the incubation was performed withPF from endometriosis patients in comparison with spermatozoaincubated in PF from the control group (12.8 ± 1.1 and12.8 ± 0.8). Similarly, the incidence of A23187-inducedacrosome reaction after 1 and 6 h of incubation (19.8 ±2.7 and 20.0 ± 2.4) was significantly (P < 0.001)lower when spermatozoa were incubated with PF from endometriosispatients in comparison with spermatozoa incubated with PF fromthe control group (34.6 ± 9.8 and 34.4 ± 1.1).The incidence of A23187-inducible acrosome reaction was alsosignificantly (P < 0.001) lower when the incubation was performedwith PF from endometriosis patients (13.1 ± 2.8 and 13.1± 2.4) when compared with that from the control group(21.8 ± 2.6 and 21.6 ± 1.5). No relationship wasfound between the stage of endometriosis and the incidence ofacrosome loss. In conclusion, the PF from endometriosis patientsdecreased both spontaneous and stimulus-induced acrosome reaction.This may represent a mechanism for the detrimental effect ofthe PF from endometriosis patients on the spermatozoa-oocyteinteraction and partially explain the aetiology of infertilityin patients with endometriosis.     

The peritoneal fluid concentration of leptin is increased in women with peritoneal but not ovarian endometriosis

This study was designed to measure leptin concentrations in the peritoneal fluid (PF) of women with different aspects of pelvic endometriosis. Among 36 consecutive women undergoing laparoscopy, nine were diagnosed as having minimal-mild endometriosis (stage I-II). Among nine other subjects with advanced stage (III-IV) disease, six showed one or more ovarian endometriotic cysts as the only operative finding. The remaining 18 unaffected women constituted the control group. Patients with endometriosis had significantly higher PF leptin concentrations (32.6 +/- 16.2 versus 17.1 +/- 6.6 ng/ml, P = 0.002); this difference remained significant when corrected for body mass index (BMI) (PF leptin/BMI ratio 1.41 +/- 0.67 versus 0.76 +/- 0.28, P = 0.001). Furthermore, the PF leptin/BMI ratio was significantly higher in women with peritoneal implants than in those in whom no implant was found at laparoscopy (1.6 +/- 0.7 versus 0.83 +/- 0.33, P = 0.007). Conversely, patients with one or more ovarian endometriomata as the only finding, had a PF leptin/BMI ratio comparable with that in women where no cyst was found (1.05 +/- 0.4 versus 1.1 +/- 0.65). In women with stage I-II endometriosis, a higher mean PF leptin/BMI ratio was found compared with those affected by stage III-IV (1.78 +/- 0.68 versus 1.05 +/- 0.43, P = 0.01). These results show that during endometriosis the presence of peritoneal disease, and not of ovarian endometriotic cysts, influences leptin concentrations in PF. The data suggest that leptin may play a role in the development of peritoneal endometriosis, and that different biochemical phenomena might be involved in the pathogenesis of the ovarian form of the disease.