Luteal phase defects in infertility patients with endometriosis

Introduction of Female Reproductive Processes and Reproductive Diseases

The female reproductive process is very complicated, including multiple processes. Each process is different and plays a vital role in reproduction. If some reproductive diseases occur, these processes will be abnormal, causing infertility problem. In this Chapter, we will describe the female reproductive process and their corresponding reproductive diseases.

What exactly is endometrial receptivity?

Endometrial receptivity is a complex process that provides the embryo with the opportunity to attach, invade, and develop, culminating in a new individual and continuation of the species. The window of implantation extends 3-6 days within the secretory phase in most normal women. In certain inflammatory or anatomic conditions, this window is narrowed or shifted to preclude normal implantation, leading to infertility or pregnancy loss. Of the factors that prevent normal implantation and pregnancy, embryo and endometrial quality share responsibility. In this review, we highlight the advances in the study of implantation from the perspective of the endometrium, normally a barrier to implantation. New advances will allow the early identification of defects in endometrial receptivity and provide new avenues for treatment that promote successful establishment of pregnancy.

Pathogenesis of endometriosis: Interaction between Endocrine and inflammatory pathways

Despite an estimated prevalence of 11% in women and plausible historical descriptions dating back to the 17th century, the etiology of endometriosis remains poorly understood. Classical theories of the histological origins of endometriosis are reviewed below. Clinical presentations are variable, and signs and symptoms do not correlate well with the extent of disease. In this summary, we have attempted to synthesize the growing evidence that hormonal and immune factors conspire to activate a local inflammatory microenvironment that encourages endometriosis to persist and elaborate mediators of its two cardinal symptoms: pain and infertility. Surprisingly, in the search for novel therapeutics for medical treatment of endometriosis, some compounds appear to have dual pharmacological functions, simultaneously modifying the endocrine and immune system facets of this complex gynecologic syndrome. We predict that these lead drugs will provide more therapeutic choices for patients in the future.

Pathogenesis of Endometriosis: Roles of Retinoids and Inflammatory Pathways

Endometriosis is a nonmalignant, but potentially metastatic, gynecological condition manifested by the extrauterine growth of inflammatory endometrial implants. Ten percent of reproductive-age women are affected and commonly suffer pelvic pain and/or infertility. The theories of endometriosis histogenesis remain controversial, but retrograde menstruation and metaplasia each infer mechanisms that explain the immune cell responses observed around the ectopic lesions. Recent findings from our laboratories and others suggest that retinoic acid metabolism and action are fundamentally flawed in endometriotic tissues and even generically in women with endometriosis. The focus of our ongoing research is to develop medical therapies as adjuvants or alternatives to the surgical excision of these lesions. On the basis of concepts put forward in this review, we predict that the pharmacological actions and anticipated low side-effect profiles of retinoid supplementation might provide a new treatment option for the long-term management of this chronic and debilitating gynecological disease.

Cigarette smoking and effects on hormone function in premenopausal women

Cigarette smoke contains compounds that are suspected to cause reproductive damage and possibly affect hormone activity; therefore, we examined hormone metabolite patterns in relation to validated smoking status. We previously conducted a prospective study of women of reproductive age (n = 403) recruited from a large health maintenance organization, who collected urine daily during an average of three to four menstrual cycles. Data on covariates and daily smoking habits were obtained from a baseline interview and daily diary, and smoking status was validated by cotinine assay. Urinary metabolite levels of estrogen and progesterone were measured daily throughout the cycles. For the present study, we measured urinary levels of the pituitary hormone follicle-stimulating hormone (FSH) in a subset of about 300 menstrual cycles, selected by smoking status, with the time of transition between two cycles being of primary interest. Compared with nonsmokers, moderate to heavy smokers (>/= 10 cigarettes/day) had baseline levels (e.g., early follicular phase) of both steroid metabolites that were 25-35% higher, and heavy smokers (>/= 20 cigarettes/day) had lower luteal-phase progesterone metabolite levels. The mean daily urinary FSH levels around the cycle transition were increased at least 30-35% with moderate smoking, even after adjustment. These patterns suggest that chemicals in tobacco smoke alter endocrine function, perhaps at the level of the ovary, which in turn effects release of the pituitary hormones. This endocrine disruption likely contributes to the reported associations of smoking with adverse reproductive outcomes, including menstrual dysfunction, infertility, and earlier menopause.

Exposure to organochlorine compounds and effects on ovarian function

BACKGROUND

Some chemicals appear to have hormonally active properties in animals, but data in humans are sparse. Therefore, we examined ovarian function in relation to organochlorine compound levels.

METHODS

During 1997-1999, 50 Southeast Asian immigrant women of reproductive age collected urine samples daily. These samples were assayed for metabolites of estrogen and progesterone, and the women's menstrual cycle parameters were assessed. Organochlorine compounds (including DDT, its metabolite DDE, and 10 polychlorinated biphenyl [PCB] congeners) were measured in serum.

RESULTS

All samples had detectable DDT and DDE, with mean levels higher than typical U.S. populations. Mean cycle length was approximately 4 days shorter at the highest quartile concentration of DDT or DDE compared with the lowest. After adjustment for lipid levels, age, parity, and tubal ligation, and exclusion of a particularly long cycle, the decrements were attenuated to less than 1 day, with wide confidence intervals (CIs). The adjusted mean luteal phase length was shorter by approximately 1.5 days at the highest quartile of DDT (95% CI = -2.6 to -0.30) or DDE (-2.6 to -0.20). With each doubling of the DDE level, cycle length decreased 1.1 day (-2.4 to 0.23) and luteal phase length decreased 0.6 days (-1.1 to -0.2). Progesterone metabolite levels during the luteal phase were consistently decreased with higher DDE concentration. PCB levels were not generally associated with cycle length or hormone parameters after adjustment, and they did not alter the DDE associations when included in the same models.

CONCLUSIONS

This study indicates a potential effect of DDE on ovarian function, which may influence other end points such as fertility, pregnancy, and reproductive cancers.

Physiopathological aspects of corpus luteum defect in infertile patients with mild/minimal endometriosis

PURPOSE

We describe a physiopathological model to the luteal insufficiency of infertile patients with mild/minimal endometriosis with normal hormone measurements in the early follicular phase.

METHODS

We designed a case-control study with 24 patients, 14 fertile with in-phase endometrium (control group) and 10 infertile with mild/minimal endometriosis and luteal insufficiency (study group). The histologic dating of endometrium was performed during cycle days 23-25 and serum TSH, FSH, LH, prolactin, and estradiol levels were measured during the early follicular phase (cycle day 3). Progesterone serum levels were measured in three different occasions during the luteal phase.

RESULTS

Patients with out-of-phase endometrium have lower estradiol levels (P = 0.031) and decreased progesterone secretion (P = 0.012) during the late luteal phase. Serum prolactin, TSH, FSH, and LH levels were similar between the groups (P > 0.05).

CONCLUSIONS

The physiopathology of luteal phase defect in infertile patients with mild/minimal endometriosis is associated with a small and large luteal cells dysfunction, characterized by abnormal follicular phase (lower estradiol serum levels) and lower progesterone LH-dependent secretion.

Effects of previous ovarian surgery for endometriosis on the outcome of assisted reproduction treatment

Endometriosis affects 2-50% of women at reproductive age. Surgery is an option for treatment, but there is no convincing evidence that it promotes a significant improvement in fertility. Also, the removal of ovarian endometrioma might lead to a reduction in the follicular reserve and response to stimulation. Therefore, the aim of this study was to evaluate the effect of previous ovarian surgery for endometriosis on the ovarian response in assisted reproduction treatment cycles and its pregnancy outcome. A total of 61 women, with primary infertility and previously having undergone ovarian surgery for endometriosis, who had received 74 IVF/intracytoplasmic sperm injection (ICSI) cycles, were studied (study group). A further 74 patients with primary infertility who underwent 77 IVF/ICSI cycles within#10; the same period of time, at the same clinic and without previous ovarian surgery or endometriosis were studied as a control group. Patients were matched for age and treatment performed. Patients </=35 years with previous ovarian surgery had fewer retrieved oocytes than the patients in the control group (P = 0.049). The number of ampoules used for ovulation induction, duration of folliculogenesis; (days), number of follicles and fertilization rate was similar in both groups. The same was observed for pregnancy rates, with 24 patients (53.3%) having had previous ovarian surgery and 27 (56.2%) in the control group becoming pregnant. Patients >35 years with previous ovarian surgery needed more ampoules for ovulation induction (P = 0.017) and had fewer follicles and oocytes than women in the control group (P = 0.001). Duration of folliculogenesis was similar in both groups, as was fertilization rate. A total of 10 patients achieved pregnancy in the study group (34.5%) and 14 (48.3%) in the control group. Although a lower pregnancy rate was observed in patients who had undergone previous ovarian surgery, this difference was not statistically significant (P = 0.424). In conclusion, ovarian surgery for the treatment of endometriosis reduces the ovarian outcome in IVF/ICSI cycles in women >35 years old, and might also decrease pregnancy rates. Therefore, for infertile patients, non-surgical treatment might be a better option to avoid reduction of the ovarian response.

Pathophysiology. The biologic principles of disease

Endometriosis, although associated with a large variety of symptoms, primarily produces pain and infertility; however, the strong correlation with these disorders, along with basic questions as to why endometriosis develops, when does it become a disease status, and why it's associated with symptoms such as pain or infertility, are still not well understood. A better understanding of the relationship between disease and symptoms of endometriosis must be acquired if effective progress in the treatment of pain and infertility related to endometriosis is to be made.

Correlation of basal menses CA-125 levels and 6 month pregnancy rates in women undergoing treatments for infertility without assisted reproductive methods

PROBLEM

The objective of this study was to evaluate the correlation of menstrual CA-125 levels with pregnancy rates (PRs) after 6 months of treatment for infertility.

METHOD

The sample consisted of a heterogenous group of 160 women who sought treatment for infertility. Treatments include progesterone supplementation, donor insemination, intrauterine insemination, and ovulation induction therapy. No laparoscopies were done during the study period. A baseline CA-125 level was drawn during menses before the initiation of therapy. Patients were followed for 6 months of treatment or until a pregnancy was achieved.

RESULTS

There was no difference in the 6 month PR or viable PR by CA-125 level.

CONCLUSIONS

Elevated CA-125 levels are not predictive of poor fertility potential at least during the first 6 months of infertility therapy. Even though these higher levels sometimes suggest that endometriosis is present, the data suggest that correction of male factor, cervical factor or ovulation factor provides effective PRs without the need for laparoscopic intervention.

Endometrial leukocyte subpopulations in women with endometriosis

The aim of this study was to investigate whether the endometrium of women with endometriosis differs immunologically from the endometrium of normal fertile women. Endometrial biopsies were obtained from 18 normal fertile women who were requesting sterilisation or reversal of sterilisation and 21 infertile women who had laparoscopically diagnosed pelvic endometriosis. The endometrial biopsies were obtained from both groups during the either early, mid or late luteal phase of the menstrual cycle. A panel of 11 monoclonal antibodies and immuno-histochemical techniques were employed to characterise the endometrial stromal leukocytes in frozen sections. Image analysis was used for semi quantitation of leukocytes. In both groups, the number of endometrial granulated lymphocytes (CD56+ CD38+ cells) and macrophages (CD68+ cells) increased significantly between the early and late luteal phase of the menstrual cycle. Compared with fertile controls, women with endometriosis had fewer T-suppressor/cytotoxic (CD8+) cells and endometrial granulated lymphocytes but more T-helper/inducer (CD4+) cells, CD68+ cells and CD16+ cells. None of these differences reached a statistically significant level. This study has shown that the endometrial lymphoid tissue of women with endometriosis does not differ qualitatively or quantitively from that of normal fertile controls. However, functional differences of endometrial leukocytes between the two groups cannot be excluded.

Management of stage III and IV endometriosis: a 10-year experience

A retrospective analysis is reported of the management of 117 cases of infertility associated with Stage III and IV endometriosis. Combined medico-microsurgical treatment was selected in 75.3% of Stage III cases and in 83.3% of those on Stage IV. Medication consisted of medroxyprogesterone acetate in 26 patients and danazol in the remaining 64. Microsurgery alone was utilized in 24.7% of Stage III patients and in 16.6% of those on Stage IV. Both surgery alone and the combined therapy had a profound positive effect on subjective symptoms: dysmenorrhea, dyspareunia and pelvic pain. Following combined therapy, pregnancy was achieved in 34.4% of all women. Respective figures are 30.7% for medroxyprogesterone acetate (29.4% Stage III and 33.3% Stage IV) and 35.9% for danazol (37.7% Stage III and 27.2% Stage IV). In the group of patients treated by surgery alone, pregnancy occurred in 25.9%. Of the pregnancies in women with Stage III endometriosis, 25 were carried to term and 6 ended with a spontaneous abortion; figures for Stage IV women are 5 and 2, respectively. Second-look laparoscopy was performed in 49 of the 79 patients who failed to conceive, at 12-36 months after treatment; persistent genital pathology, to which infertility could be attributed, was found in 77.5% of them.

Endometriosis-associated infertility

Despite intense clinical interest and increasingly sophisticated diagnostic techniques, we know surprisingly little of the relationship between endometriosis and infertility or the mechanism of infertility in these couples. No therapy specifically directed toward the ectopic endometrial implants, medical or surgical, has been demonstrated to improve the likelihood of pregnancy for couples with endometriosis-associated infertility. This is consistent with the observation that, in the absence of mechanical distortion of the pelvic viscera, no therapy directed against the implants improves the likelihood of pregnancy in these couples. The reason for this lack of progress is most probably that the mechanism of infertility in these couples remains to be determined. At present, it would be more accurate to say that these couples have unexplained infertility. The most promising therapeutic approach is to treat women with endometriosis-associated infertility with a non-specific cycle fecundity enhancing technique. Typically this is one of the newer assisted reproductive technologies such as controlled ovarian hyperstimulation with intrauterine insemination of capacitated sperm. Since the fecundity of many of the women with endometriosis in the later reproductive years is rapidly declining, this may represent their most cost-effective option for establishing a pregnancy. Only with further effort directed towards determining the mechanisms of infertility in these couples will a more effective therapy be forthcoming.

Endometriosis and luteal phase defect

It has been reported that there exists a correlation between endometriosis and the luteal phase defect (LPD) as one of the determinants in infertility. In some theories, the hampered maturation of the corpus luteum is believed to be caused by the reduction of LH receptors, increase in prolactin, prostaglandin and macrophages in endometriosis. The purpose of this clinical study is to prove the hypothesis that there exists a significant correlation between endometriosis and the luteal phase defects in infertility. The samples were taken at random from 150 women with infertile marriages on whom ovulation was assumed to have occurred, from January 1981 to December 1985. The assumption that there might have occurred ovulation is determined through the observation of their basal body temperature (BBT) chart. Endometrium biopsies to diagnose the LPD were taken at the end of their luteal phase. A laparoscopy examination to diagnose the pelvic endometriosis was done in the following cycle. Of 84 patients with endometriosis, 44 (55.4%) had luteal phase defects, while the remaining 40 (47.6%) patients had no luteal phase defects. Of the 66 patients without endometriosis, 27 (40.9%) had luteal phase defects, while the remaining 39 (59.1%) did not have luteal phase defects. These differences were not significant (p > 0.05). In summary, this clinical study fails to show the existence of significant correlation between endometriosis and the luteal phase defect.

Luteal function in infertile patients with endometriosis

OBJECTIVE

Our purpose was to determine whether infertile patients who have endometriosis show luteal phase defects.

STUDY DESIGN

The luteal function in 24 infertile patients who had endometriosis was compared with the luteal function in 20 patients who had unexplained infertility and did not have endometriosis (control). In both groups serum luteinizing hormone, follicle-stimulating hormone, progesterone, and estradiol were assayed every day throughout the menstrual cycle. Endometrial biopsy specimens were obtained from eight patients of the endometriosis group for histologic dating of the endometrium.

RESULTS

No significant differences in progesterone levels were observed between these two groups during the mid and late luteal phase. Seven of the eight patients who underwent histologic dating showed a luteal phase pattern, whereas only one patient was out of phase.

CONCLUSION

Infertile patients who have endometriosis do not always have luteal phase defects.

Comparison of endometrial biopsy and urinary pregnanediol glucuronide concentration in the diagnosis of luteal phase defect

To determine if pregnanediol glucuronide (PG) excretion is useful in luteal phase assessment, we compared daily first morning urinary PG concentrations during the luteal phase in nine normal and nine deficient cycles. Total luteal pregnanediol excretion (44.1 +/- 11.3 versus 64.0 +/- 11.6 area units +/- SEM) was not different. However, significantly less pregnanediol was excreted by the abnormal group during the 1st 5 days of the luteal phase (12.7 +/- 1.2 versus 18.0 +/- 1.7 area units +/- SEM, respectively). Thus, delayed PG excretion may be characteristic of luteal phase defect and measurement of urinary PG may be useful only if daily samples during the early luteal phase are obtained.

Endometriosis and infertility

The relationship of endometriosis, the most common benign gynaecological disease during reproductive life, to infertility is generally ill understood. The association between infertility and minimal to mild endometriosis, when no anatomical defect is evident, may be explained by the following possible mechanisms: alternations in peritoneal fluid (macrophages - immunoglobulins, Interleukin-1, protease inhibitors, prostanoids, an ovum capture inhibitor), ovulatory dysfunctions (anovulation, LUF syndrome), luteal phase defect, disturbed implantation, and spontaneous abortion. These possibilities are discussed. The latest prospective controlled studies offer strong evidence that endometriosis per se is not a direct cause of infertility. On the other hand, the disease usually deteriorates if not treated, and therefore medical or surgical interventions are often needed when expectant treatment or other infertility therapies, e.g., ovulation induction, fail to result in pregnancy. Women with minimal to mild endometriosis only should be diagnosed as having unexplained infertility, which today may be treated by in vitro fertilization.

In vitro fertilization and embryo transfer (IVF/ET): an established and successful therapy for endometriosis

The purpose of this report is to present a 6-year experience in the management of endometriosis with in vitro fertilization and embryo transfer (IVF/ET). We divided 136 patients who underwent 280 cycles into three groups: (1) previous history of endometriosis but normal pelvis at the time of oocyte retrieval, (2) stages I-II endometriosis (revised AFS classification), and (3) stages III-IV endometriosis. The stimulation protocols, estradiol (E2) responses, and distribution of terminal E2 patterns were similar in all groups. Group 3 had significantly fewer preovulatory and immature oocytes retrieved and fewer embryos transferred. The fertilization rate and the per cycle/per transfer pregnancy rates were similar in all groups. The miscarriage rate was higher in group 3, and the ongoing pregnancy rate per cycle was lower. Luteal phase E2 and progesterone levels were comparable in all groups. No differences were found when groups 2 and 3 were analyzed for the presence of one or two ovaries or the presence/absence of ovarian endometriosis. The overall fertilization rate, the per cycle/per transfer pregnancy rates, and the miscarriage rate were similar to those of tubal factor patients. We underscore the excellent outcome of patients with minimal or mild endometriosis in IVF/ET. We conclude that patients with moderate or severe endometriosis have a compromised reproductive potential, probably because of a reduced oocyte recovery rate and poor embryo quality.

Hormonal profiles and embryo quality in women with severe endometriosis treated by in vitro fertilization and embryo transfer

A study was undertaken comparing the outcomes of 30 women with infertility due to untreated severe (grade IV) pelvic endometriosis with a comparable series of 28 women whose infertility was caused solely by irreversible tubal disease. There were no significant differences in either the follicular phase or luteal phase hormonal profiles of estradiol and progesterone, but there was a significantly reduced pregnancy rate in those women with severe endometriosis. In part, this was due to the recovery of fewer oocytes from the endometriosis patients (P less than 0.001) despite the fact that the peak estradiol levels and ovarian accessibility were similar in the two groups. However, there were no significant differences in the proportion of oocytes that fertilized or the number that demonstrated normal embryo growth and high-grade embryo quality. There also appears to be an implantation inhibitory factor in patients with severe endometriosis as the pregnancy rate/embryo transferred and number of gestational sacs identified/embryo transferred were significantly reduced (P less than 0.05).

Luteal phase dysfunction in endometriosis: elevated progesterone levels in peripheral and ovarian veins during the follicular phase

Endometriosis has been associated with corpus luteum inadequacy and abnormalities of luteal phase progesterone (P) secretion. In this study, abnormal luteolysis, as a second factor of luteal dysfunction, was assessed in 13 women with endometriosis and 25 control patients by measurement of ovarian vein estradiol (E2) and P during the follicular phase. The results reveal that women with endometriosis have (1) significantly lower ovarian vein E2, (2) significantly higher both peripheral and ovarian vein P, and (3) threefold higher P/E2 ratios than controls during the follicular phase. These data support the concept of continued P production from an active corpus luteum well into the follicular phase of the following cycle in women with endometriosis. Failure of adequate luteolysis is a second aspect of luteal dysfunction in endometriosis and strongly supports the growing body of data confirming ovulatory asynchrony in the minimal; endometriosis infertility syndrome.

Protein, progesterone, and protease inhibitors in uterine and peritoneal fluids of women with endometriosis

This study was undertaken to determine whether women with endometriosis have altered protein, progesterone (P), and protease inhibitor concentrations in their uterine fluid and peritoneal fluid (PF) compared with controls at different phases of the menstrual cycle. Uterine flushings (UFs), PF, and blood were obtained during the follicular and luteal phases of the cycle from 29 normal women and 16 women who were diagnosed as having endometriosis. Protein content in UF did not change significantly throughout the cycle in either group. However, PF protein in patients with endometriosis was significantly (P less than 0.05) higher than in controls during the luteal phase. Total UF P was significantly (P less than 0.05) reduced in women with endometriosis during the late luteal phase. During the early luteal phase, trypsin inhibitory activity in UF from normal women was significantly (P less than 0.05) higher than at any other phase of the cycle, whereas inhibitory activity in UF from patients with endometriosis remained relatively constant. Patients with endometriosis had significantly (P less than 0.05) higher total activity in PF during the early luteal phase than did controls. These results indicate that women suffering from endometriosis have significantly lower levels of P and less protease inhibitor within their uterine cavity during the luteal phase of the cycle, and significantly higher concentrations of protein and protease inhibitor in PF during the luteal phase.

Follicle growth patterns and endocrinological abnormalities in infertile women with minor degrees of endometriosis

Eighteen patients whose only demonstrable cause of infertility was a minor degree of endometriosis and whose partners were normal, were investigated prospectively for one menstrual cycle using ultrasonography and endocrine profiles. Twelve cycles appeared to be normal. A luteinized unruptured follicle (LUF) occurred in two cycles and one patient had a follicular cyst. In a further two patients there was inadequate or abnormal folliculogenesis whilst in the last patient the follicle ruptured prematurely. This study describes the variety of endocrinological abnormalities found in women with mild endometriosis, and concludes that, in this series at least, there is a low frequency of LUF.

Endometriosis

Endometriosis is a common disease associated with pelvic pain and infertility. The etiology and physiology are poorly understood, often frustrating clinicians and patient. Treatment may be medical or surgical, or a combination of these. Nursing care involves education of couples about endometriosis and its physical and psychological implications.

Endometriosis: a reappraisal of pathogenesis and treatment

The enigmatic disease of endometriosis continues to baffle both the scientist and the clinician. An encompassing theory of pathogenesis has failed to emerge from contemporary understanding of the immunologic manifestations, the hormonal aberrations, or the evasive infertility associated with endometriosis. Similarly unsettling is the failure of medical or conservative surgical maneuvers to eradicate endometriosis in a manner commensurate with castration. It is hoped that further insight into these areas of research will resolve both of these dilemmas.

The role of in vitro fertilization in infertile patients with endometriosis

Thirty-nine cycles were studied in patients with a history of endometriosis who went through in vitro fertilization. In 15 cycles, there was no evidence of endometriosis; in 10 cycles, the patients had mild or moderate disease; in 14 cycles, severe or extensive endometriosis was found. The pregnancy rates per cycle were 33%, 60%, and 7%, respectively (groups I and II, no significant difference; groups II and III, P less than 0.01). The difference was due to the different number of oocytes aspirated at laparoscopy because of technical problems in the cases with severe and extensive disease. There was also a significant difference in the number of pregnancies per transferred cycles. There was no difference in the luteal phase in the three groups. The reproductive potential, which seemed to be similar in groups I and II, was severely impaired in the group with severe endometriosis.

Luteinizing hormone receptor disorder in endometriosis

Luteinizing hormone (LH) receptor concentrations in ovarian follicles and corpora lutea were measured in 51 patients with histologically proven endometriosis and in 41 control patients. The LH receptor concentrations in cases of endometriosis were lower during the early (0.43 +/- 0.11 [mean +/- standard error] versus 1.31 +/- 0.27 fmol/mg protein; P less than 0.001) and late (0.48 +/- 0.10 versus 1.59 +/- 0.22 fmol/mg protein; P less than 0.001) follicular phase, and during the late luteal phase (2.62 +/- 0.55 versus 4.62 +/- 0.65 fmol/mg protein; P less than 0.05) of the cycle than in control patients. In contrast to the control patients, the LH receptor concentration during the follicular phase remained constant in endometriosis, being lower in patients with extensive or severe disease than in patients with moderate or mild disease (0.28 +/- 0.07 versus 0.61 +/- 0.21 fmol/mg protein; P less than 0.05). Endometriosis-associated infertility might be a consequence of a defect in the mechanism mediating LH action in the ovaries.