It is clear that endometriosis is associated with infertility. Indeed, the incidence of infertility in patients with endometriosis may range from 20%

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1 FERTILITY AND STERILITY Copyright 1984 The American Fertility Society Vol. 41, No.1, January 1984 Printed in U.SA. Etiology of infertility in monkeys with endometriosis: luteinized unruptured follicles, luteal phase defects, pelvic adhesions, and spontaneous abortions* Robert S. Schenken, M.D.t:j: Ricardo H. Asch, M.D.:j: Robert F. Williams, Ph.D.11 Gary D. Hodgen, Ph.D.1I University of Texas Health Science Center at San Antonio, San Antonio, Texas, and National Institute of Child Health and Human Development, Bethesda, Maryland To elucidate the etiology of infertility due to endometriosis, we autografted endometrial or adipose tissue to the pelvic peritoneum of 21 cynomolgus monkeys. These primates were divided into five groups: control animals with adipose tissue autografts (n = 5), animals with microscopic endometriosis (n = 5), animals with mild endometriosis (n = 5), animals with moderate endometriosis (n = 4), and animals with severe endometriosis (n = 2). During three subsequent menstrual cycles, each animal underwent (1) serial assay of peripheral serum gonadotropins and steroids; (2) mating timed according to daily serum 17f3-estradiol; and (3) laparotomy to document an ovulatory stigma. The chemical and term pregnancy rates were lower among monkeys with moderate or severe endometriosis, as compared with control animals. The impaired fertility in monkeys with endometriosis appeared to be mediated primarily by failure of follicular rupture and/or pelvic adhesions. Fertil Steril41:122, 1984 It is clear that endometriosis is associated with infertility. Indeed, the incidence of infertility in patients with endometriosis may range from 20% Received July 18, 1983; revised and accepted August 24, *Supported in part by NICHD Clinical Investigator Award HD trecipient of ACOG-ORTHO Academic Training Fellowship. :j:department of Obstetrics and Gynecology, Division of Human Reproduction, University of Texas Health Science Center at San Antonio. Reprint requests: Robert S. Schenken, M.D., Department of Obstetrics and Gynecology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, Texas IIPregnancy Research Branch, National Institute of Child Health and Human Development, National Institutes of Health. 122 Schenken et al. Infertility in monkeys with endometriosis to 60%.1, 2 In spite of the apparent association of infertility and endometriosis, there is a paucity of evidence to identify a clear cause-and-efiect relationship, or to clarify the specific mechanism(s) of infertility due to this enigmatic disease. Recently, numerous investigators have proposed several interesting but disparate hypotheses to explain the cause of infertility in patients having endometriosis. 3 These hypotheses, based on both clinical and animal studies, have suggested that the following factors may be responsible: anovulation, luteal phase defects (LPDs), hyperprolactinemia, pelvic adhesions, luteinized unruptured follicle (LUF) syndrome, autoimmune phenomena, and spontaneous abortion. 3-9 Although each of the proposed factors is supported by some persuasive evidence, no single mechanism has been established as the primary cause of infertility. Fertility and Sterility

2 In view of this persistent controversy over the etiology of infertility in patients with endometriosis, we evaluated the reproductive performance of monkeys in which endometriosis had been surgically induced. The purpose of this report is to describe the observed effect(s) of endometriosis on fertility and discuss the specific mechanism(s) involved. MATERIALS AND METHODS Twenty-one adult female cynomolgus monkeys (Macaca fascicularis) demonstrating menstrual regularity were selected for the study. Housing, feeding, and general husbandry practices have been described previously.lo SURGICAL INDUCTION OF ENDOMETRIOSIS Using ketamine (Vetalar, Parke-Davis, Morris Plains, NJ) anesthesia (15 mglkg), blood was collected daily on days 8 to 14 of the menstrual cycle via venipuncture and serum assayed for 17f3-estradiol (E2) by radioimmunoassay (RIA).l1 Laparotomy, using the same anesthetic, was then performed 3 to 5 days after a clearly defined preovulatory peak in serum E2. All animals with obvious pelvic adhesions or without an ovulatory stigma were excluded from the study. A l-cm vertical fundal hysterotomy was done and mg of endometri urn was dissected from the myometriurn and placed in sterile 0.9% saline. The uterine incision was then closed in one layer with 4-0 Vicryl (Ethicon, Somerville, NJ) suture. In all animals, the endometrial tissue was minced and injected subperitoneally into the vesicouterine fold, uterine incision, right and left broad ligaments, and cul-de-sac. In ten animals, the endometrial tissue was discarded, and - 1 gm of omental adipose tissue was resected, minced in sterile 0.9% saline, and injected into the same five sites. The abdominal incision was then closed in layers. During the subsequent menstrual cycle, laparotomy was performed 3 to 5 days after the midcycle E2 surge. The presence of viable endometrial and adipose tissue and the extent of adhesion formation were noted. The endometrial and adipose tissue implants were biopsied, and the tissue was fixed in 10% formalin for histologic examination after hematoxylin and eosin staining. The American Fertility Society classification for pelvic endometriosis,12 modified to correct for the smaller size of the pelvic organs in the monkey, was used to stage the disease. FERTILITY STUDIES During three subsequent menstrual cycles, blood was collected every other day during the early follicular and luteal phases of the cycle and daily on cycle days 8 to 14. Blood samples were discontinued at the time of the next menses or, in the absence of menses, on cycle day 42. The serum was frozen at - 15 C until assayed for luteinizing hormone (LH), follicle-stimulating hormone (FSH), E2, and progesterone (P) by RIAP An aliquot of serum was obtained from all periovulatory samples for daily E2 determination. RIA for macaque chorionic gonadotropin (mcg) was performed on all blood samples after cycle day All females were time-mated for 2 to 3 days with males of proven fertility. Matings were conducted near midcycle, beginning on the first day after the peak in the serum E2. Cycles with inappropriately timed matings were excluded. Laparotomy was performed 3 to 5 days after the preovulatory peak in serum E2 in each subsequent study cycle. Pelvic findings were recorded in detail, and the presence or absence of a stigma of ovulation was noted. In the absence of menses and with a positive mcg, rectal palpation was performed (after 40 to 45 days of gestation) to confirm continuation of an intrauterine pregnancy. Pregnancies were allowed to progress to term without subsequent intervention. Cycles were defined as ovulatory when an ovulatory stigma was present and serum P levels were> 3 ng/ml from 5 to 10 days after the LH surge.14 Absence of a stigma of ovulation in association with luteal phase serum P levels> 3 ng/ ml was the criterion used to document an LUF. Cycles were defined as anovulatory when luteal phase serum P levels remained <: 3 ng/ml and no ovulatory stigma was present. LPD was defined in cases where the luteal phase length was < 10 days and the P secretion (integrated area under the curve) < 50% of the mean for all study cycles. Luteal phase mcg values > 50 jj-g/ml were considered chemical pregnancies. 13 To determine the effect of pelvic adhesions on fertility, we correlated the location of moderate or severe peritubal or periovarian adhesions with the location of the corpus luteum during each ovulatory cycle. A specific cycle was recorded as having adhesions only when peritubal or periovarian adhesions were present ipsilateral to the corpus luteum. Vol. 41, No.1, January 1984 Schenken et ai. Infertility in monkeys with endometriosis 123

3 Figure 1 Photomicrograph of endometrial implant in one monkey with moderate endometriosis. Notice the presence of both endometrial glands and stroma (hematoxylin and eosin, original magnification, x 100). STATISTICAL ANALYSIS The Fisher exact probability test was used to compare menstrual cycle characteristics and pregnancy rates. Student's t-test was used to determine differences in duration of the follicular and luteal phase endocrine profiles and gonadotropin and steroid secretion (area under the curve). A difference was considered statistically significant when its P value was < RESULTS MACROSCOPIC AND MICROSCOPIC EXAMINATION Macroscopic examination confirmed the presence of viable tissue in all 11 monkeys with endometrial autografts. The implants ranged in size from 1 to 4 mm in diameter and appeared as wellvascularized reddish nodules or hemosiderin-like deposits. Two animals developed cystic adnexal masses that contained hemorrhagic, thick fluid ("chocolate cysts"). Pelvic adhesions were present in varying degrees. Most animals developed "puckering" of the peritoneum surrounding the implants, fine peri tubal or peri ovarian adhesions, or dense fibrotic adnexal adhesions. Using a modification of The American Fertility Society classification, the endometriosis was staged as mild in five animals, moderate in four, and severe in two. Microscopic examination of implants in all 11 animals revealed endometrial glands and stroma (Fig. 1). Hemosiderin-laden macrophages and areas of fibrosis were often observed. Endometrial cyst walls were lined with low cuboidal epithelium and sparse endometrial glands. Macroscopic examination of adipose tissue autografts revealed the presence of normal-appearing vascularized tissue that was indistinguishable from surrounding subperitoneal fat. Adhesions were noted to involve the uterine incision and omentum in several animals. Adnexal adhesions developed in only one animal. Microscopic examination of fat implants showed normal adipose tissue in five monkeys and evidence of endometrial glands or hemosiderin-laden macrophages, usually near the fundal scar, in five animals. These animals were classified as controls with adipose tissue only (n = 5) and animals with microscopic endometriosis (n = 5). MENSTRUAL CYCLE CHARACTERISTICS AND ENDOCRINE PROFILES The total number of cycles studied and cycle characteristics for each group are presented in Table 1. The number of cycles studied was similar Table 1. Total Number of Study Cycles in Which Monkeys Were Time-Mated and Incidence of Ovulation, Anovulation, LUF, andlpd Group Total cycles Ovulatory cycles a Anovulatory cycles b Adipose tissue (79%) Endometriosis Microscopic (80%) Mild 11 9 (82%) Moderate 11 5 (46%) Severe 6 3 (50%) aluteal phase serum P > 3 ng/ml, ovulatory stigma present. bluteal phase serum P < 3 ng/ml, ovulatory stigma absent. CLuteal phase serum P > 3 ng/ml, ovulatory stigma absent. dluteal phase length < 10 days and P secretion < 50% of mean for all cycles. ep < 0.01 versus animals with adipose tissue implants. fall five cycles with an LUF demonstrated an LPD. 1 (7%) 1 (6%) 2 (18%) 1 (9%) 0(0%) LUF" LPD d 0(0%) 2 (14%) 0(0%) 2 (13%) 0(0%) 0(0%) 5 (46%)e 5 (46%)f 3 (50%)' Schenken et al. Infertility in monkeys with endometriosis Fertility and Sterility

4 0) e o 2E Ill' 0)0' Ole... o a... ::j 27.6! ! ~ 0.7 o,--,--,,-,-,--,--,--,-, :~~~ o I I I I I I I I I Days Figure 2 Endocrine profile and duration of follicular and luteal phases during ovulatory cycles in control monkeys with adipose tissue autografts, excluding those monkeys having microscopic endometriosis (total cycles, 11). in all groups when corrected for the number of animals in each group. The percentage of ovulatory cycles was similar in control monkeys (79%) and monkeys with microscopic endometriosis (80%) and mild endometriosis (82%). However, monkeys with moderate and severe endometriosis demonstrated a lower incidence of ovulatory cycles, 46% and 50%, respectively; the difference was due solely to the greater incidence of L UF in these monkeys. The endocrine profiles and duration of the follicular and luteal phases during ovulatory cycles in control monkeys (Fig. 2) and animals with mild, moderate, or severe endometriosis (Fig. 3) demonstrated no significant differences in the following: (1) follicular or luteal phase lengths; (2) serum gonadotropins as determined by follicular phase LH/FSH ratio or follicular phase LH and FSH secretion; (3) midcycle LH and FSH surge; and (4) serum steroids as determined by midcycle E2 peak or luteal phase E2 and P secretion. LUTEINIZED UNRUPTURED FOLLICLE AND INADEQUATE LUTEAL PHASE An LUF was noted in five often cycles in monkeys with moderate endometriosis and three of six cycles in animals with severe disease. An LUF was never present in control animals or animals with microscopic and mild endometriosis. The incidence of an LUF was significantly greater (P < 0.01) in animals with moderate and severe endometriosis, as compared with control animals (Table 1). Cycles with an LUF were never associated with a serum mcg > 50 j.lg/ml or clinical evidence of pregnancy. Although each individual monkey with moderate and severe endometriosis demonstrated an LUF during at least one study cycle, the occurrence of LUF was random. That is, in an individual animal, a cycle with an LUF might be followed by a cycle with an obvious ovulatory stigma, or vice versa. The size or location of endome- 3l ::j 27.0 ~ :0.7 o ~, ~ r ~l::j~ o,,-,--,-.--,-,--,-,-, :Q_ 300 j "0 E 200 e, ~ g 100 0) e o 2E Ill' 0)0' e a... Ole o I, 1 I j 15 ':,.,..',,,, b Days Figure 3 Endocrine profile and duration of follicular and luteal phases during ovulatory cycles with ovulatory stigma in monkeys having mild, moderate, or severe endometriosis (total cycles, 17). Vol. 41, No.1, January 1984 Schenken et al. Infertility in monkeys with endometriosis 125

5 -, ,--,-...,.--,--,---, 15 j :': :': :':1.2 o.r---,-,-----,------,-----,--,--,-----, ::j~ o I I I I, u~::j~~ o I I I r I I r I Q) e o ~E Q)0l "'... Ole o... a j 10 5 o I 1 fa" Days Figure 4 Endocrine profile and duration of follicular and luteal phases during cycles with an LUF without LPD in monkeys having moderate and severe endometriosis (total cycles, 3). trial implants or pelvic adhesions did not correlate with the occurrence of an LUF, except in one animal. In this monkey, an ovarian endometri- 0ma was noted adjacent to an LUF during two study cycles. An LPD was present in five of the eight cycles with an LUF. The endocrine profiles of cycles with an LUF, but without an LPD, are presented in Figure 4. There was no significant difference in these cycles, as compared with normal ovulatory cycles, with regard to follicular phase length, FSH/LH ratios, LH or FSH secretion, midcycle E2 surge, the "preovulatory" peak of LH and FSH, luteal phase length, or P and estrogen secretion in the luteal phase. Similarly, the endocrine profile in monkeys with an LUF and LPD demonstrated no significant endocrine abnormalities, except for shortened luteal phases and diminished P secretion (Fig. 5). An LPD was noted during two cycles in the group with adipose tissue implants and two cycles in the group with microscopic endometriosis. However, none of these cycles was associated with an LUF. PELVIC ADHESIONS Significant pelvic adhesions were present in 3 of 11 cycles in the adipose tissue group, 3 of 5 cycles in monkeys with moderate endometriosis, and 2 of 3 cycles in monkeys with severe endometriosis. None of the cycles resulted in a term intrauterine pregnancy (Table 2). When adnexal adhesions were not present ipsilateral to the corpus luteum, there was no significant difference in pregnancy rates between the control group with adipose tissue (38%) and the endometriosis group (33%). CHEMICAL AND TERM PREGNANCY In each of the groups of monkeys with adipose tissue, microscopic endometriosis, and mild endometriosis, three of five monkeys carried a pregnancy to term. In contrast, only one of six animals IE ::j..j~ ~ 5 o rl 23.2:':1.3, 14..0:': :,: ,--,-.-,--,-,~ ~l::~~ o Ir-~-.--'--'-'--'--'--' ~E e... :::~ ~ g 100 o '-1 Q) 5 GiE 1n... Q)0l Ole... o a... ::1 Jr-"'.. r-.r-?"r... ~~...--.::..-TI --" Days Figure 5 Endocrine profile and duration of follicular and luteal phases during cycles with both an LUF and LPD in monkeys exhibiting moderate endometriosis (total cycles, 5). 126 Schenken et al. Infertility in monkeys with endometriosis Fertility and Sterility

6 Table 2. Effect of Pelvic Adhesions on Term Pregnancy Rates During Ovulatory Cycles. Ovulatory cycles Group Ovulatory cycles" with adhesions b Adipose tissue 11 3 Endometriosis Microscopic 12 0 Mild 9 0 Moderate 5 3 Severe 3 2 aluteal phase serum P > 3 nglml, ovulatory stigma present. b Adhesions present ipsilateral to the corpus luteum. cpercentage of ovulatory cycles with adhesions. dno adhesion or adhesion contralateral to the corpus luteum. epercentage of ovulatory cycles without adhesions. Term intrauterine Ovulatory cycles Term intrauterine pregnancies c without adhesions d pregnancies' 0(0%) 8 3 (38%) 0(0%) 12 3 (27%) 0(0%) 9 3 (33%) 0(0%) 2 1 (50%) } 33'Ji 33% 0(0%) 1 0(0%) " } with moderate or severe endometriosis delivered at term. A luteal phase serum meg> 50 ~g/ml was detected in 18 of the 57 study cycles (Table 3). The incidence of a chemical pregnancy was similar in monkeys with adipose tissue implants, microscopic endometriosis, and mild endometriosis. The lower chemical pregnancy rate in animals with moderate and severe endometriosis was statistically significant, as compared with control animals with adipose tissue (P < 0.05). Ten of the 18 cycles with a diagnosed chemical pregnancy resulted in a term intrauterine pregnancy, suggesting that embryonic death occurred in 8 fertile menstrual cycles. The incidence of pregnancy loss was not significantly different among the groups, and none of the animals demonstrated clinical evidence of spontaneous abortion or preterm delivery.. DISCUSSION The rat, rabbit, and monkey have been used to study the effect of endometriosis on fertility Although each model has specific advantages with respect to availability, cost, and other factors, the monkey offers distinct advantages, in that (1) endometriosis can be surgically induced with a high success rate and (2) the reproductive functions of monkeys are very similar to those of human beings, allowing more realistic extrapolation of findings to the clinical setting. In this study, surgical induction of endometriosis was successful in all animals autografted with endometrial tissue. Histologic examination of the implants demonstrated endometrial glands and stroma in all cases. Animals with adipose tissue autografts did not develop macroscopic endometriosis; however, implants in five of ten animals were noted to have microscopic foci of endometrial glands and stroma. This may represent either coelomic metaplasia or inadvertent spill of endometrial tissue at the time of hysterotomy and resection of endometrial tissue. The incidence of anovulatory cycles in control monkeys and monkeys with endometriosis was similar when anovulation was determined by absence of an ovulatory stigma and luteal phase serum P levels < 3 ng/ml. Previous studies in human beings have suggested an increased incidence of anovulatory cycles with all stages of endometriosis. Soules et al. 4 described a 17% incidence of ovulatory disturbance in women with endometriosis, and Acosta et al. 18 reported a 27% Table 3. Chemical (Luteal Phase Serum mcg > 50 MlmlJ and Term Pregnancy Rates During Ovulatory Cycles Luteal phase mcg > 50 JLg/ml Term intrauterine pregnancies Group Total cycles (% of total cycles) (% of mcg > 50 JLg/ml) Adipose tissue 14 6 (42) 3 (50) Endometriosis Microscopic 15 6 (40) 3 (50) Mild 11 4 (36) 3 (75) Moderate 11 1 (9) } 12%a 21% 1 (100) } } 50% Severe 6 1 (17) 0(0) Total (32) 10 (56) ap < 0.05 versus animals with adipose tissue implants. } 67% Vol. 41, No.1, January 1984 Schenken et ai. Infertility in monkeys with endometriosis 127

7 incidence of anovulation in 107 women with endometriosis. The lower incidence of assigned anovulation in our study may have resulted from the separate classification of anima :Is with an LUF and LPD. The "LUF syndrome" describes an infertile woman with regular menses and presumptive evidence of ovulation but without release of an ovum. Brosens et a1. 6 observed this phenomenon at laparoscopy in 21 % of patients with endometriosis but in only 6% of control patients. These authors also reported that peritoneal fluid E2 and P levels were 5 to 20 times lower than those found in women with normal ovulatory cycles, suggesting that the follicular fluid with its high steroid concentration was not released into the peritoneal cavity. However, this relationship ofluf to infertility with endometriosis remains speculative:.other investigators have demonstrated a similar incidence of LUF in patients with and without endometriosis.19 This discrepancy may be due to the timing of laparoscopy; that is, the laparoscopy may have been performed after the stigma had undergone epithelial regeneration. It is clear from our findings that an LUF frequently occurred in monkeys with moderate endometriosis (46%) and severe endometriosis (50%). Because an LUF was not observed in animals with adipose tissue autografts, microscopic or mild endometriosis, or in cycles prior to the induction of moderate or severe endometriosis, it appears that an LUF is a major cause of infertility in monkeys with endometriosis. In animals with'severe endometriosis, an LUF was noted in two cycles involving the same ovary bearing an endometrioma. Apart from this animal, however, the location of the endometriosis or pelvic adhesions did not correlate with the occurrence of an LUF. Furthermore, the occurrence of an LUF was sporadic in monkeys with endometriosis and not consistently present inconsecutive cycles. The role of LPD in infertility with endometriosis is unclear. Grant,20 in his study ofluteal function in women with endometriosis, reported that 45% of patients had evidence of LPD. Hargrove and Abraham21 also demonstrated that mean P levels were lower and E2 levels were higher during the luteal phase of women with endometriosis. However, others19,22 have argued that the corpus luteum in women with endometriosis is not defective. In our study, an LPD was noted during two cycles in control animals, two cycles in animals with microscopic endometriosis, and five 128 Schenken et ai. Infertility in monkeys with endometriosis cycles in animals with moderate endometriosis. In monkeys with moderate endometriosis, an LUF was present in all cycles with LPD. Interestingly, the aberrant follicular phase endocrine profile normally found in monkeys with LPD was not present in monkeys with endometriosis and LPD. 14 Pelvic adhesions in patients with endometriosis may affect fertility by preventing ovum pickup or gamete transport. This cause-and-effect relationship is difficult to refute in patients with moderate or severe endometriosis and extensive pelvic adhesions. In our study, no term pregnancies resulted when adnexal adhesions were noted on the same side as the ovary having the ovulatory stigma. In contrast, when adnexal adhesions were not present, the incidence of a term pregnancy was similar in monkeys with endometriosis and in control monkeys with adipose tissue implants. These preliminary findings suggest that when normal follicular rupture occurs in monkeys with endometriosis, it is the location of pelvic adhesions and not endometriosis per se that impairs fertility. Recent studies in women with mild endometriosis23,24 have demonstrated that pregnancy rates after expectant management are similar to pregnancy rates after medical or surgical therapy. In one study,23 75% of patients with mild endometriosis conceived in 1 year without treatment, as compared with 72.4% of patients treated with conservative surgery. Our data support this interpretation in that collective chemical pregnancy rates per cycle in animals with microscopic endometriosis (40%) and mild endometriosis (36%) were not significantly different from the term pregnancy rate in control animals (42%). In contrast, chemical pregnancy rates were lower in animals with moderate and severe endometriosis and in association with the highest incidence of LUF and pelvic adhesions. In addition to the lower incidence of chemical pregnancies in animals with moderate and severe endometriosis, monkeys in these groups demonstrated a lower incidence of term pregnancies per cycle, compared with control animals. Although the mechanism of this reduced apparent early pregnancy rate is unknown, it may be related to an increase in peritoneal fluid macrophages. These cells have a higher capacity to phagocytize human spermatozoa than do macrophages from women without endometriosis,7, 8 and may reduce fertility by preventing fertilization. Fertility and Sterility

8 The incidence of spontaneous abortion in patients with endometriosis is reported to be increased. Petersohn 9 reported a spontaneous abortion rate of 22% in women with endometriosis and noted a significant drop in the spontaneous abortion rate following conservative surgery. Naples et a1. 25 also noted that the spontaneous abortion rate declined following conservative surgery or medical therapy for endometriosis. In our study, monkeys with mild, moderate, and severe endometriosis were noted to have luteal phase serum meg values consistent with conception during six cycles. Because only four term intrauterine pregnancies occurred, we estimated that the spontaneous abortion rate was 33%. In animals with adipose tissue implants and microscopic endometriosis, 6 of 12 cycles having meg values> 50 j-tg/mlresulted in term pregnancies, or aspontaneous abortion rate of 50%. The high incidence of spontaneous abortion in 'both the endometriosis and control groups may be due to the small sample size. However, based on our limited observation, the presence of endometriosis in monkeys did not appear to increase the incidence of spontaneous abortion. In summary, we have described the surgical induction of endometriosis in monkeys. This primate model for endometriosis seems well suited to study the mechanisms of infertility associated with endometriosis. Here, impaired fertilization and term pregnancy rates in monkeys with endometriosis were apparent only in association with moderate or severe disease. Our prellminary findings suggest that impaired fertility is mediated by failure of follicular rupture (LUF) and pelvic adhesions; however,unidentified factors that inhibit fertilization may also be important. LPDs in the absence of anluf, anovulation, and spontaneous abortion were not principal factors contributing to infertility specifically in monkeys with endometriosis. Acknowledgments. The technical skills of Don Barber, Adrian Coleman, Dick Greenawalt, James Lewis, Almorris Lynch, Barbara Murphy, and Charles Turner, and the typing assis. tance of Linda Gonzales are greatly appreciated. REFERENCES 1. McGoogan LS: Sterility and endometriosis. Arch Surg 49:437, Kistner RW: Endometriosis and infertility. In Progress in Infertility, Second edition, Edited by SJ Behrman, RW Kistner. Boston, Little,Brown & Co., 1968, p Muse KN, Wilson EA: How does mild endometriosis cause infertility? Fertil Steril 38:145, Soules MR, Malinak LR, Bury R, Poindexter A: Endometriosis and anovulation: a coexisting problem in the infertile female. Am J Obstet Gynecol 125:412, HirschowitzJS, Soler NG, Wortsman J: The galactorrheaendometriosis syndrome. Lancet 1:896, Brosens la, Koninckx PR, Corvelyn P A: A study of plasma progesterone, oestradiol 1713, prolactin and LH levels, and of the luteal phase appearance of the ovaries in patients with endometriosis and infertility. Br J Obstet Gynaecol 85:246, Haney AF, Muscato JJ, Weinberg JB: Peritoneal fluid cell populations in infertility patients. Fertil Steril 35:696, Haney AF, Muscato JJ, Weinberg JB: Sperm phagocytosis by human peritoneal macrophages: a possible cause of infertility in endometriosis. Presented at the Twenty Eighth Annual Meeting of the Society for Gynecologic Investigation, March 18 to.21, 1981, St. Louis, Missouri. Abstract Petersohn L: Fertility in patients with ovarian endometriosis before and after treatment. Acta Obstet Gynecol Scand 49:331, Goodman AL, Descalzi CC, Johnson DK,Hodgen GD: Composite pattern of circulating LH, FSH, estradiol and progesterone during the menstrual cycle in cynomolgus monkeys. Proc Soc Exp BiolMed 155:479, Marut EL, Williams RF, Cowan BD, Lynch A, Lerner SP, Hodgen GD: Pulsatile pituitary gonadotropin secretion.during maturation of the dominant follicle in monkeys: estrogen positive feedback enhances the.biological activity of LH. Endocrinology 109:2270, American Fertility Society: Classification of endometriosis. Fertil Steril 32:633, HodgenGD, TullnerWW, VaitukaitisJL, WardDN,Ross GT: Specific radioimmunoassay of chorionic gonadotropin during implantation in rhesus monkeys. J Clin Endocrinol Metab 39:457, Wilks JW, Hodgen GD, Ross GT: Endocrine characteristics of ovulatory and anovulatory menstrual cycles in the rhesus monkey. In Human Ovulation, Edited by ESE Hafez. Amsterdam, Elsevier-North Holland Biomedical Press, 1979, p Vernan MW, Graves K, Jawad MJ, Wilson EA:The surgical induction of endometriosis in the rat. Presented at the Thirtieth Annual Meeting of the Society for Gynecologic Investigation, March 17 to 20, 1983, Washington, D.C. Abstract Schenken RS, Asch RH: Surgical induction of endometriosis in the rabbit: effects on fertility and concentrations of peritoneal fluid prostaglandins. Fertil Steril 34:581, dizerega GS, Barber DL, Hodgen GD: Endometriosis: role of ovarian steroids in initiation, maintenance, and suppression. Fertil Steril 33:649, Acosta AA, Buttram VC, Besch PK, Malinak LR, Franklin RR, Vanderheyden JD: A proposed classification of pelvic endometriosis. ObstetGynecol 42:190, Dmowski WP, Rao R, Scommegna A: The luteinized unruptured follicle syndrome and endometriosis. Fertil Steril 33:30, Grant A: Additional sterility factors in endometriosis. Fertil Steril 17:514, 1966 Vol. 41, No.1, January 1984 Schenken et.al. Infertility in monkeys with endometriosis 129

9 21. Hargrove JT, Abraham GE: Abnormal luteal function in endometriosis. Fertil Steril (Abstr) 34:302, Wentz AC: Premenstrual spotting: its association with endometriosis but not luteal phase inadequacy. Fertil Steril 33:605, Schenken RS, Malinak LR: Conservative surgery versus expectant management for the infertile.patient with mild endometriosis. Fertil Steril 37:183, Seibel MM, Berger MJ, Weinstein FG, Taymor ML: The effectiveness of danazol on subsequent fertility in minimal endometriosis. Fertil Steril 38:534, Naples JD, Batt RE, Sadigh H: Spontaneous abortion rate in patients with endometriosis. Obstet Gynecol 57:509, Schenken et al. Infertility in monkeys with endometriosis Fertility and Sterility