The value of pre-treatment with gonadotrophin releasing hormone (GnRH) analogue in IVF-ET therapy of severe endometriosis

Controversy concerning the optimal treatment of endometriosis and its related infertility still exists. Thirty-one women with moderate and severe endometriosis, who failed to conceive during previous in-vitro fertilization and embryo transfer (IVF-ET) cycles (protocol A), were re-admitted for the procedure following a period of hormonal suppression with a gonadotrophin releasing-hormone (GnRH) agonist (protocol B). Following GnRH analogue treatment, a significantly higher number of oocytes were recovered (P less than 0.0006); consequently more embryos were transferred and significantly higher clinical pregnancy rates per cycle (P less than 0.0001) were achieved. This difference may be directly related to the beneficial effect of the GnRH analogue on pelvic endometriosis, converting severe cases into mild ones with improved ovarian accessibility and probably oocyte quality.     

Randomized clinical trial of a levonorgestrel-releasing intrauterine system and a depot GnRH analogue for the treatment of chronic pelvic pain in women with endometriosis

BACKGROUND: The objective of this multicentre randomized, controlled clinical trial was to compare the efficacy of a levonorgestrel-releasing intrauterine system (LNG-IUS) and a depot-GnRH-analogue in the control of endometriosis-related pain over a period of six months. METHODS: Eighty-two women, 18 to 40 years of age (mean 30 years), with endometriosis, dysmenorrhoea and/or CPP, were randomized using a computer-generated system of sealed envelopes into either LNG-IUS (n = 39) or GnRH analogue (n = 43) treatment groups at three university centres. Daily scores of endometriosis-associated CPP were evaluated using the Visual Analogue Scale (VAS), daily bleeding score was calculated from bleeding calendars, and improvement in quality of life was evaluated using the Psychological General Well-Being Index Questionnaire (PGWBI). The pain score diary was based on the VAS in which women recorded the occurrence and intensity of pain on a daily basis. A monthly score was calculated from the result of the sum of the daily scores divided by the number of days in each observation period. RESULTS: CPP decreased significantly from the first month throughout the six months of therapy with both forms of treatment and there was no difference between the groups (P > 0.999). In both treatment groups, women with stage III and IV endometriosis showed a more rapid improvement in the VAS pain score than women with stage I and II of the disease (P < 0.002). LNG-IUS users had a higher bleeding score than GnRH-analogue users at all time points of observation with 34% and 71% of patients in the LNG-IUS and GnRH-analogue groups, respectively, reporting no bleeding during the first treatment month, and 70% and 98% reporting no bleeding during the sixth month. No difference was observed between groups with reference to improvement in quality of life. CONCLUSIONS: Both, the LNG-IUS and the GnRH-analogue were effective in the treatment of CPP-associated endometriosis, although no differences were observed between the two treatments. Among the additional advantages of the LNG-IUS is the fact that it does not provoke hypoestrogenism and that it requires only one medical intervention for its introduction every 5 years. This device could therefore become the treatment of choice for CPP-associated endometriosis in women who do not wish to conceive.     

Effect of GnRH analogues on apoptosis and expression of Bcl-2, Bax, Fas and FasL proteins in endometrial epithelial cell cultures from patients with endometriosis and controls

BACKGROUND: Our purpose was to evaluate the effect of the GnRH agonist (GnRHa), leuprolide acetate (LA), and the GnRH antagonist (GnRHant), Antide, on apoptosis and expression of apoptosis-related proteins in endometrial epithelial cell (EEC) cultures from patients with endometriosis and controls (infertile women without endometriosis). METHODS: Biopsy specimens of eutopic endometrium were obtained from 22 patients with endometriosis and from 14 women that served as controls. Apoptosis was examined in EEC after incubation with LA and Antide. Bax, Bcl-2, Fas and FasL expression was evaluated after exposure to LA, Antide or a combination of both. The percentage of apoptotic cells (%ApC) was assessed by the acridine orange-ethidium bromide technique, and protein expression was evaluated by western blot and immunocytochemistry. RESULTS: LA 100 and 1000 ng/ml increased the %ApC in EEC from patients with endometriosis (both P < 0.05) and controls (p < 0.05 and P < 0.01, respectively). Antide 10(-5) M increased the %ApC in EEC from patients with endometriosis and controls (P < 0.01). In EEC from women with endometriosis, Bax expression increased after treatment with LA, Antide and LA + Antide (P < 0.05, P < 0.001 and P < 0.001), whereas Bcl-2 expression decreased after exposure to LA and Antide (P < 0.001 and P < 0.01). FasL expression increased after LA, Antide and LA + Antide treatments (P < 0.01, P < 0.001 and P < 0.01). No significant changes were observed on Fas expression. CONCLUSIONS: GnRH analogues enhanced apoptosis in EEC, and this was accompanied by an increase in expression of the pro-apoptotic proteins Bax and FasL and a decrease in expression of the anti-apoptotic protein Bcl-2.     

One year comparison between two add-back therapies in patients treated with a GnRH agonist for symptomatic endometriosis: a randomized double-blind trial

BACKGROUND: It has been proposed that hormonal supplementationduring prolonged GnRH agonist therapy prevents hypoestrogenicside effects, including bone loss. The optimal combination forlong-term treatments with safe metabolic profile remains questionable.A norprogesterone derivative, promegestone, was assessed forthe first time in a double-blind trial. METHODS: Seventy-eightpatients with endometriosis with rAFS (Revised American Societyfor Reproductive Medicine) scores of III–IV were randomlyassigned to monthly leuprorelin 3.75 mg (1 year) which,after the third injection was used in combination with promegestone0.5 mg (P) plus either estradiol placebo (PL) or estradiol2 mg (E) per day. Bone mineral density (BMD) was determinedat baseline, 6 and 12 months, and biological and clinical quarterlyassessments were performed. Analysis was by the intention totreat method. RESULTS: At month 12, BMD changes from baselinewere –6.1 ± 3.7 and –4.9 ± 4.0%in the PL-P group, at the spine and hip, respectively. Thisbone loss was prevented in the E-P group: –1.9 ± 3.1and –1.4 ± 2.3%, respectively (P < 0.0001inter-group comparisons). The BMD decrease in the E-P groupwas explained by the changes occurring during the first 6 monthsof treatment. There was no deleterious change in lipid parameters.Clinical improvement was observed without an inter-group difference.CONCLUSIONS: Estradiol 2 mg and promegestone 0.5 mgper day is an effective and safe add-back therapy, which canbe proposed for prolonged leuprorelin treatment over 6 monthsin severe endometriosis.     

Possible implication of midkine in the development of endometriosis

BACKGROUND: The present study was conducted to assess whether midkine (MK), a multifunctional molecule known to stimulate tumor growth, may be involved in the development of endometriosis. METHODS: The mitogenic activity of MK on cultured endometriotic stromal cells was examined by measuring 5-bromo-2'-deoxyuridine (BrdU) incorporation. Concentrations of MK in the peritoneal fluid (PF) of women without or with endometriosis and those under GnRH agonist treatment were measured using a specific enzyme immunoassay. The expression of MK mRNA in peritoneal bone marrow-derived cells, peritoneum and endometriotic tissues was evaluated by RT-PCR. RESULTS: MK significantly increased BrdU incorporation into the DNA of cultured endometriotic stromal cells. The MK concentrations in the PF of the women with advanced endometriosis (stages II, III and IV) Median: 1.21 ng/ml; interquartile range 0.80-2.27 were significantly higher than those of the women without endometriosis and with stage I endometriosis (0.06 ng/ml, 0.67-1.26, P < 0.05). As for the menstrual phase, the MK concentration in PF in the inteal phase (1.32 ng/ml. 0.72-2.21) were significantly higher than those in the follicular phase (0.95 ng/ml, 0.68-1.24, P < 0.05). In addition, women with adnexal adhesions had higher concentrations of MK in PF than those without adhesions (P < 0.05). The MK concentrations of the women under GnRH agonist treatment were significantly lower than those of the other groups (P < 0.001). The expression of MK mRNA was detected in peritoneal bone marrow-derived cells, peritoneum and endometriotic tissues. CONCLUSIONS: The present findings suggest that MK may play roles, such as stimulation of endometriotic cell proliferation, in the development of endometriosis.     

Misrouted cell surface GnRH receptors as a disease aetiology for congenital isolated hypogonadotrophic hypogonadism

GnRH plays an essential and central role in neuroendocrine control of reproductive function. The GnRH receptor is located on the plasma membrane of gonadotrophs, pituitary cells that synthesize the gonadotrophins LH and FSH. This receptor belongs to the superfamily of G protein-coupled receptors, and is preferentially coupled to the G(q/11) protein; its activation by GnRH analogues stimulates the synthesis and release of LH and FSH. Resistance to GnRH by inactivating (loss-of-function) mutations of the human GnRH receptor leads to distinct forms of sporadic or inherited hypogonadotrophic hypogonadism. Although in vitro expression of a number of these mutated GnRH receptors in heterologous systems has shown that these mutations appear to alter several functions of the molecule, including ligand binding, receptor activation or interaction with coupled effectors, recent observations from our laboratory have challenged this view and indicated that protein misfolding and resultant misrouting is a mechanism that, by itself, may lead to loss of function of the human GnRH receptor. In this review we describe the experimental data that led us to this conclusion and how these studies revealed previously unsuspected features of the mutant human GnRH receptor.     

Endometriosis: Hormonal regulation of endometriosis and the rationales and effects of gonadotrophin-releasing hormone agonist treatment: a review

The knowledge about the role of oestrogen in the regulationof endometriosis growth and symptoms has been reviewed. Studieson oestrogen and progesterone metabolism and receptivity inendometriotic tissue and the impact on growth regulation andclinical symptoms of steroidal hormones are discussed. Theseinclude tissue sample assays, ex-vivo tissue culturing as wellas clinical studies concerning the effect of different hormonaltreatment. All studies published on steroid receptors in endometriotictissue have shown lower levels of oestrogen and progesteronereceptors in endometriotic tissue than in uterine endometrium.These data might, at least partly, explain the poor clinicalresponse to hormonal treatment experienced in some cases. However,in cases of hormone-sensitive endometriotic tissue, a completeovarian inactivation is not important, as comparable reducingeffects on lesions and symptoms are seen after various hormonaltreatments leading to a varying degree of ovarian inactivation.A less pronounced hypo-oestrogenism during treatment gives lesssevere consequences for the future, mainly concerning the bonemass and the circulation, and might allow a prolonged symptom-freeperiod on low-dose treatment when needed. Not all cases of endometriosisare receptive to hormonal treatment.     

Prediction of endometriosis with serum and peritoneal fluid markers: a prospective controlled trial

BACKGROUND: The objective of this prospective controlled trial was to investigate the ability of a group of serum and peritoneal fluid (PF) markers to predict, non-surgically, endometriosis. METHODS AND RESULTS: Serum and PF samples were obtained from 130 women while undergoing laparoscopy for pain, infertility, tubal ligation or sterilization reversal. Concentrations of six cytokines [interleukin (IL)-1beta, IL-6, IL-8, IL-12, IL-13 and tumour necrosis factor (TNF)-alpha] were measured in serum and PF, and reactive oxygen species (ROS) in PF, and levels were compared among women who were allocated to groups according to their post-surgical diagnosis. Fifty-six patients were diagnosed with endometriosis, eight with idiopathic infertility, 27 underwent tubal ligation or reanastomosis (control group) and 39 were excluded due to bloody PF. Only serum IL-6 and PF TNF-alpha could be used to discriminate between patients with and without endometriosis with a high degree of sensitivity and specificity (P < 0.001). A threshold of 15 pg/ml PF TNF-alpha provided 100% sensitivity and 89% specificity (positive likelihood ratio of 9.1 and negative likelihood ratio of 0). A threshold of 2 pg/ml for serum IL-6 provided a sensitivity of 90% and specificity of 67% (positive likelihood ratio of 2.7 and negative likelihood ratio of 0.14). CONCLUSIONS: By measuring serum IL-6 and PF TNF-alpha, it was possible to discriminate between patients with endometriosis and those without. Before these markers can be used as a non-surgical diagnostic tool, these data should be verified in a larger study.     

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.     

Effect of endometriosis on early embryonic development in the rabbit

The reasons for sub-fertility in patients with mild endo-metriosisremain unclear. Peritoneal fluid constituents may alter tubaltransport and embryonic cleavage, with subsequent implantationdisturbances. We used an animal model to study the influenceof endometrial implants on early embryonic development. In 25rabbits, endometrium from the right uterine horn was transplantedonto the peritoneum (Experimental group = Group E). In 25 rabbits,fat was transplanted (control group = Group C). After a recoveryperiod of 12 weeks the does were mated, and killed 24 h later.In the experimental group the implants had changed into cystsof 5–15 mm in diameter. Histological examination revealedendometrial glands and stroma in every specimen. Periadnexaladhesions did not develop in any animal. No marked differenceswere found between Groups E and C in embryonic cleavage stage,24 h after mating. Additional culturing of the embryos for 48h in a suitable culture medium revealed normal further developmentof the embryos. Bearing in mind the restrictions of extrapolatinga rabbit model to the human, it is suggested that the decreasedfecundity in mild endometriosis is not caused by altered earlyembryonic cleavage rate. The results of this study offer indirectevidence for implantation disturbances as a cause of endometriosis-associatedsub-fertility.     

Phenotypic and functional studies of leukocytes in human endometrium and endometriosis

The aetiology of endometriosis, a common and disabling disorder, is presently unknown, although immune dysfunction could allow ectopic endometrial fragments to survive outside the uterine cavity. These studies investigate the relationship between leukocyte populations, steroid hormone receptor expression, proliferative activity, bcl-2 expression and apoptosis in eutopic and ectopic endometrium from women with endometriosis or adenomyosis at different phases of the menstrual cycle. Significantly increased oestrogen receptor expression, bcl-2 expression and numbers of CD8+ leukocytes were found in ectopic compared with eutopic endometrium in endometriosis, and CD56+ endometrial granulated lymphocytes (eGLs) were significantly reduced in ectopic endometrium. Apoptotic cells were rarely found in control and subject endometria. In contrast with endometriosis, adenomyotic lesions showed identical steroid hormone receptor expression, proliferative activity, bcl-2 expression and leukocyte subpopulations to eutopic endometrium, indicating different aetiologies for these disorders. The unusual CD56+ CD16- eGLs present in large numbers in late secretory phase eutopic endometrium were highly purified (>98%) by immunomagnetic separation. Except for a negligible cytotoxic activity of eGLs from early proliferative samples, cytotoxic activity of eGLs from non-pregnant endometrium during the menstrual cycle was comparable with those in peripheral blood, predominantly CD56+ CD16+ natural killer cells. eGLs from non-pregnant endometrium and early pregnancy showed a variable proliferative response to 5 and 100 U/ml interleukin-2 over 48-h and 120-h time courses. eGLs are evidently functionally important in the eutopic endometrium. Their absence in endometriotic lesions together with increased CD+8 T-cell numbers and increased oestrogen receptor and bcl-2 expression may have significant effects on the development and progression of endometriosis.     

GnRH agonist as luteal phase support in assisted reproduction technique cycles: results of a pilot study

BACKGROUND: The aim of the study was to investigate whether intranasal (IN) administration of a GnRH agonist could provide luteal support in IVF/ICSI patients. METHODS: Controlled ovarian hyperstimulation (COH) was performed using hMG/FSH and a GnRH antagonist. Patients were then randomly allocated to either 10,000 IU hCG, followed by vaginal administration of micronized progesterone (3x 200 mg/day) (group A), or 200 microg IN buserelin followed by either 100 microg every 2 days (group B), or 100 microg every day (group C), or 100 microg twice a day (group D), or 100 microg three times a day (group E). Luteal support was continued for 15 days. RESULTS: Twenty-three patients were randomized. Groups B and C were discontinued prematurely in view of the short luteal phase. The luteal phase was significantly shorter in groups B, C and D, whereas group E was comparable with group A, 13.5 and 13.0 days, respectively. In the mid-luteal phase, median progesterone levels were significantly lower in groups B, C and D, whereas group E was comparable with group A, 68.9 and 98.0 ng/ml, respectively. Estradiol (E2) was significantly reduced in groups B and D but sustained in group E. In the hCG group, LH levels were undetectable (<0.1 IU/l), whereas LH was detectable and significantly higher in groups C, D and E. Two pregnancies were obtained in the hCG group (two of five), one ectopic and one ongoing. Three pregnancies were obtained in group E, one miscarriage and two ongoing twin pregnancies (three of five). CONCLUSION: IN administration of buserelin may be effective in triggering follicular maturation and providing luteal phase support in patients undergoing assisted reproduction techniques (ART).     

Treatment with anti-TNF monoclonal antibody (c5N) reduces the extent of induced endometriosis in the baboon

BACKGROUND: Inflammatory cytokines, including interleukin (IL)-1, IL-6, IL-8 and tumour necrosis factor-alpha (TNF-alpha), are important in the pathogenesis of endometriosis. We assessed the efficacy of anti-TNF monoclonal antibody (mAb, c5N), known to prevent induced endometriosis in baboons, in reducing established endometriosis in baboons. METHODS: This prospective, randomized, blinded, controlled study was conducted in baboons at the Institute of Primate Research (IPR), Nairobi, Kenya. Endometriosis was induced in 18 adult female baboons (Papio anubis) with regular menstrual cycles and a normal pelvis; the extent of endometriosis was documented by videolaparoscopy 25 days later. The baboons were then randomly assigned to receive a single infusion of either placebo (n=7, 5 ml/kg) or c5N (n=11, 5 mg/kg). Follow-up laparoscopy was performed 25 days later to document any differences in the number, surface area and estimated volume of lesions between the two groups and between the first and the second laparoscopies in each group. Representative biopsies of at least one endometriotic lesion per baboon were obtained at the final laparoscopy. RESULTS: Significant reductions in total surface area, estimated total volume of endometriotic lesions and both number and surface area of red lesions were observed after treatment with c5N, but not after placebo treatment, when compared to the initial laparoscopy. Conversely, a significant increase in the number of typical and red lesions was observed after placebo treatment when compared to the initial laparoscopy. Neither c5N nor placebo treatment affected the menstrual cycle. CONCLUSION: In baboons with induced endometriosis, anti-TNF-mAb (c5N) treatment significantly reduced the extent of endometriosis, mainly due to reducing both the number and surface area of red lesions. These findings suggest that anti-TNF-mAb therapy may have therapeutic potential for active peritoneal endometriosis.     

Endometriosis: Oestrogen and progesterone receptors in endometriosis: heterogeneity of different sites

The expression of receptors for the ovarian steroid hormonesoestrogen and progesterone was studied immunohisto-chemicallyusing monoclonal antibodies in samples of endometriosis andendometrium in 22 patients. In nine patients samples of endometriosisfrom more than one site were studied. There was marked heterogeneityin expression of receptors in endometriosis, both when comparinglesions with the corresponding endometrium and also betweensamples of endometriosis collected from different sites withinthe same patient. It wa ssuggested that local environmentalfactors related to the site deotg abd degree if fibrosis ofthe lesions determine the amount of steroid hormone stimylationreaching the lesions and account for the observed differencebetween endometriosis and endometrium and between endometriosislesions of different sites.     

Effect of neonatal treatment with a GnRH antagonist on development of the cell-mediated immune response in marmosets.

PROBLEM: We examined the effect of neonatal treatment with a gonadotropin-releasing hormone (GnRH) antagonist (antide) on the development of cell-mediated immunity in male marmosets. METHOD OF STUDY: Neonatal marmoset twins were treated with either vehicle or antide, and the proliferative response (PR) of lymphoid tissue to mitogens was assessed during infancy, the peripubertal period, and adulthood. RESULTS: Basal proliferation of peripheral blood mononuclear cells (PBMC) from treated peripubertal twins was elevated above control values, but the PR of the cells to T and B cell mitogens was subnormal. Conversely, PBMC from treated infants exhibited an enhanced PR to some of the mitogens employed. In vitro culturing of thymocytes (control or treated) from the three developmental stages with either antide or a GnRH agonist increased basal proliferation, but decreased the PR to mitogens by 60-80%. CONCLUSION: Neonatal treatment with antide alters development of, but does not permanently impair, cell-mediated immunity in the marmoset. GnRH appears to modulate immune responses throughout development in the primate.     

L1 cell adhesion molecule (L1CAM) as a pathogenetic factor in endometriosis

BACKGROUND: Endometriosis is a benign and progressive disease with a highprevalence. Women with endometriosis, especially with atypicalendometriosis, have a higher probability for developing ovariancancer compared with women without endometriosis. The L1 celladhesion molecule (L1CAM) is over expressed in ovarian and endometrialcarcinomas and is associated with a bad prognosis. Here, wehave analysed L1CAM expression in endometriosis. METHODS AND RESULTS: In our study with the samples from 79 patients with, and 37patients without, endometriosis, we found that endometriosiscell lines and short-term cultures of endometrium from womenwith endometriosis expressed L1CAM at the mRNA and protein level.Quantitative RT-PCR analysis showed that L1CAM was expressedat significantly higher level in the epithelial compartmentfrom patients with endometriosis compared with healthy controls(P = 0.0126). By immunohistochemical staining, 15 of 31 ovarianendometriotic lesions (48%) were shown to have L1CAM-positivestaining. Of these 15 L1CAM-positive samples, 13 were atypicalendometriotic lesions. Soluble L1 present in the conditionedmedium of epithelial endometrium cultures from women with endometriosiswas able to stimulate neurite outgrowth as measured in a chickenganglion assay. CONCLUSIONS: We propose that L1CAM could promote endometriosis developmentby increasing enervation and aggravation. L1CAM expression ishigher in atypical endometriosis compared with normal 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.     

Matrix metalloproteinase-9 and tissue inhibitor of matrix metalloproteinase-1: a possible role in the pathogenesis of endometriosis

BACKGROUND: Matrix metalloproteinases (MMPs) are a family of endopeptidases which play a role in the degradation and turnover of extracellular matrix proteins. Their action is regulated by specific tissue inhibitors called tissue inhibitors of metalloproteinases (TIMPs). METHODS: We measured the concentrations of total and active MMP-9 in peritoneal fluid of infertile women with mild or moderate endometriosis (n = 22) and compared them with those in a control group of infertile patients (n = 21). RESULTS: We found that the mean (+/-SD) total concentrations of MMP-9 in the peritoneal fluid of patients with endometriosis was 6.2 +/- 1.8 ng/ml, in comparison with 2.9 +/- 2.6 ng/ml in the control group (P = 0.001). Concentrations of active MMP-9 did not differ significantly between the groups. The concentrations of TIMP-1, after logarithmic transformation, were significantly lower (P = 0.017) in endometriotic peritoneal fluids than in peritoneal fluid of control women, 1.02 +/- 0.21 ng/ml and 1.16 +/- 0.18 ng/ml respectively. No correlation between stage of disease, steroid hormone concentration, MMP-9 (total and active) and TIMP-1 was found. CONCLUSIONS: These results suggest that a disturbed equilibrium exists between MMP-9 and TIMP-1 in peritoneal fluid of women with endometriosis. This may play an important role in the pathogenesis of the disease.