Karolinska Hospital, Stockholm, Sahlgrenska Hospital, Gothenburg, Sweden, and University Hospital, Geneva, Switzerland

Transcription

1 FERTILITY AND STERILITY Copyright The American Fertility Society Vol. 56, No. 5, November 1991 Printed on acid-free paper in U.S.A. Comparative morphometric study of the endometrium, the fallopian tube, and the corpus luteum during the postovulatory phase in normally menstruating women* Taeja Kim-Bjorklund, M.D.t Britt-Marie Landgren, M.D., Ph.D.t Lars Hamberger, M.D., Ph.D.:j: Elizabeth Johannisson, M.D., Ph.D. Karolinska Hospital, Stockholm, Sahlgrenska Hospital, Gothenburg, Sweden, and University Hospital, Geneva, Switzerland Objective: To compare function and histologic structure of the corpus luteum (CL) to the morphology of the endometrium and the fallopian tube in normally menstruating women. Design: Circulating steroid and luteinizing hormone (LH) levels were compared with CL steroid production in vitro and the histology of CL, endometrium, and the fallopian tube at four stages of the postovulatory phase (days LH±O/LH +3, LH +4/LH +7, LH +8/LH + 11, LH + 12/onset of menstruation). Setting of Patients: The study included 28 volunteers with proven fertility undergoing surgical sterilization timed in relation to the LH surge. Interventions: Blood and urine samples for LH, progesterone (P), and estradiol assessment were obtained before (simultaneously with ultrasound examinations), during, and after operation. Biopsy specimens from CL, endometrium, and fallopian tube were taken at the surgical sterilization and subjected to morphometric analyses. Main Outcome Measures and Results: Significant correlation was found between the endometrial dating and the LH surge (r = 0.923) and between the dating of the endometrial and CL biopsies (r = 0.918). A significant correlation (P < 0.01) existed between circulating P levels and two endometrial indices; the number of vacuolated cells (LH +4/LH +7) and the glandular diameter (LH +8/LH + 11). Conclusion: In normally menstruating women, the endometrial biopsy is likely to closely gauge the CL activity provided the biopsy is timed in relation to the LH surge. Fertil Steril 56:842, 1991 Received December 12, 1990; revised and accepted July 5, *Supported by the World Health Organization's Special Programme of Research, Development and Research Training in Human Reproduction, Geneva, Switzerland, the International Committee for Research in Reproduction, Geneva, Switzerland, and by grant nr from the Swiss National Research Foundation Switzerland. t Department of Obstetrics and Gynecology, Karolinska Hospital. :j: Department of Obstetrics and Gynecology, Sahlgrenska Hospital. Reprint requests: Elizabeth Johannisson, M.D., Ph.D., Clinic of Sterility and Gynecologic Endocrinology, Hopital Cantonal, Geneva, Switzerland. In the postovulatory phase of the normal menstrual cycle, the endometrium is undergoing anumber of precise histologic changes induced by the steroids produced by the corpus luteum (CL). It is generally believed that the morphological changes occurring in the endometrium is closely gauging the CL activity particularly during the first 6 days after ovulation. 1 -a An endometrial biopsy is therefore often used as a diagnostic tool in women with unexplained infertility. For instance, the diagnosis of luteal phase defect (LPD) as a cause of sub fertility or infertility is usually based on a retarded development of the endometrium. 842 Kim-Bjorklund et al. Compare endometriumfcl function Fertility and Sterility

2 However, the reported incidence of retarded endometrial development varies between 4% to 65% among women with unexplained infertility, 4 ~ and the correlation between the dating of the endometrium and that of the CL can therefore be questioned. An analysis of the progesterone (P) receptors does not seem to improve the diagnosis. In women having retarded endometrial development, assessed by histologic dating, the concentration of P receptors has been found to vary between higher than, 7 the same as,8 or lower than 9 in women with normally developed endometrium. In part, this controversy of the concepts of the LPD could be explained by the lack of objective methods in assessing the morphology of the endometrium and the CL. The aim of the present study is therefore to use morphometric measurements in comparing the morphology of the endometrium and the CL obtained at different phases of the postovulatory phase. Furthermore, the cyclic changes that may occur also in the fallopian tube have not been as yet objectively assessed. The present study therefore includes a comparison between the histologic structure of the endometrium, the fallopian tube, and the CL in the postovulatory phase of women with regular menstrual cycles. To statistically evaluate the validity of this comparison, the histologic material is analyzed by morphometric methods allowing quantitative objective measurements. Subjects MATERIALS AND METHODS Twenty-eight apparently healthy volunteers, 29 to 42 years of age (mean of 36 years), with proven fertility and regular menstrual cycles (25 to 35 days) participated in the study. The average weight was 61 kg (range of 48 to 90 kg), and the height was varying between 152 and 179 em (mean of 165 em). They were all undergoing surgical sterilization on their own request as a method of contraception. None of the women had used steroidal contraceptives or an intrauterine device during the 6 months preceding the surgical intervention. None of them had had an abortion within the last 6 months or a delivery within 12 months before admission to the study. As to previous reproductive events, 27 women had given birth to at least one living child (9 women had 3 or more live births, 14 had 2, and 4 women had just llive birth). Nineteen women had had at least 1 abortion (4 had 3 or more interruption of preg- nancies, 5 women had 2, and 10 women 1 abortion). Before the surgery, all women had a complete gynecological examination (including a Papanicolaou smear). Sampling of Material for Biochemical and Histologic Analysis All women participating in the study were undergoing laparotomy for sterilization by tubal ligation. At the surgical intervention, biopsies were obtained from the endometrium, the fallopian tube, and the CL. The women were all subjected to ultrasound (US) scanning and luteinizing hormone (LH) measurements in the urine to determine the LH peak. Starting on cycle day 8, US examinations were carried out three to five times in the preovulatory phase. Simultaneously with the US examination, urine and blood samples were obtained. The LH levels were determined by two methods; radioimmunoassay (RIA) on plasma samples or enzyme immunoassay on early morning urine specimens. Six women were operated on days LH 0 to LH +3, six other women were operated on days LH +4 to LH +7. A third group of patients was operated on days LH+8 to LH+ll, and finally, a fourth group consisting of six women had an operation between LH + 12 and the day of the onset of menstruation. The endometrial biopsies were obtained with a Randall curette (Stille-Werner, Stockholm, Sweden) without dilatation of the cervix. The biopsies of the fallopian tube and the CL were all obtained during their laparotomy. At the time of the surgical intervention, the CL was identified and removed. A part of this material was fixed for light microscopic examination, and the other part was processed for in vitro incubation studies. 10 All biopsy specimens were immediately fixed in Bouin's solution, embedded in paraffin, sectioned, and stained in hematoxylin eosin. The material was then subjected to morphometric analysis. In addition to the blood samples (10 ml) withdrawn three to five times during the follicular phase, blood samples were taken on the day of the LH peak and on the day before the operation. Samples were also withdrawn at the day of the surgical intervention and on the 1st and 2nd day after the operation. The blood samples were immediately centrifuged and the plasma frozen and stored at -20 C until processed. Morphometric Analyses Endometrium The morphometric analysis of the endometrium was carried out by histometric and stereologic Vol. 56, No. 5, November 1991 Kim-Bjorklund et al. Compare endometriumfcl function 843

3 methods. 2 3 Ten arbitrarily chosen microscopic fields were analyzed in each biopsy specimen. For the morphometric assessment, a light microscope (Type Olympus BH.2; Imtec, Uppsala, Sweden) equipped with wide angle eye pieces (12.5X) and a micrometer disk was used. The measurements were all carried out at a magnification of 500X (objectives X40). In each microscopic field, the following indices were assessed: (1) the number of transversally sectioned glands (expressed in glands per mm 2 ); (2) the number of glandular mitoses (expressed as number of mitoses per 1,000 glandular cells); (3) the number of stromal mitoses (expressed as number of mitoses per 1,000 stromal cells); (4) the diameter of the glandular lumen of the transversally sectioned glands (expressed in #Lm); (5) the glandular epithelial height (expressed in #Lm); (6) the number of vacuolated cells (expressed as basal vacuolated cells per 1,000 glandular cells); (7) the pseudostratification of the glandular epithelium (expressed by the following scoring system: 1 = none, 2 = slight, 3 =moderate, and 4 = marked); (8) the secretion of the glands (expressed according to the scoring system indicated above); (9) the stromal edema (expressed according to the scoring system indicated above); (10) the predecidual reaction (expressed according to the scoring system indicated above); and (11) the leukocytic infiltration (expressed according to the scoring system indicated above). The dating of the endometrium, based on the indices mentioned above, was carried out according to Johannisson et al. 3 Fallopian Tube Morphometric measurements were also carried out on the fallopian tube. In this material two indices were measured: (1) the epithelial height (expressed in #Lm) and (2) the subepithelial edema (expressed according to the scoring system indicated above). Corpus Luteum The CL was dated according to the classification system originally proposed by Corner 11 and later modified by Novak and WoodruffP The dating of the CL involves a gradual transition from one stage to another and therefore a day-to-day dating cannot be done. In the present study, four different stages were identified: stage 1: the early phase of CL characterized by the presence of blood clot without centrally organized structure; stage 2: the vascular phase showing thin-walled blood vessels penetrating the granulosa layer; stage 3: the stage of maturity with a broad lutein zone traversed by trabeculae of theca interna (theca lutein or paralutein cells) and several blood vessels; and stage 4: the regression phase characterized by increase in lipids and increasing fibrosis. In Vitro Incubation Studies A part of the CL biopsy was used for in vitro incubation according to the method described by Kim Bjorklund et al. 10 The production of estradiol (E 2) and P was assessed by RIA methods in the incubating medium after 24 and 48 hours of incubation. Hormone Assays The E 2 and P levels of the peripheral blood were measured by RIA methods according to Aso et al. 13 Luteinizing hormone was analyzed using World Health Organization reagents. 14 The results were expressed in terms of the International Reference Preparation 68/40. Statistical Methods For the calculation of means, confidence limits, regression, correlation, and AN OVA with appropriate contrasts, statistical methods described by Snedecor and Cochran 15 were used. In most calculations, the log-normal distribution of data was applied. 16 The data were therefore converted to common logarithms before the calculations. Geometric means and confidence limits were obtained by antilogarithming the logarithmic values. Ethical Aspects By informed consent all volunteers recruited for the investigation agreed to participate. The objectives of the study were carefully explained, and the participants were allowed to withdraw from the study at any time. Permission to conduct the study was granted by the Ethics Committee of the Karolinska Hospital, Stockholm, Sweden. RESULTS Blood samples and surgically removed biopsies from the endometrium, the fallopian tubes, and the CL were obtained in 28 patients. Figure 1 shows the relationship between the endometrial dating and the days of the luteal phase related to the LH surge. A highly significant correlation was found between these two variables (r = 0.923). Based on the highly 844 Kim-Bjorklund et al. Compare endometrium/cl function Fertility and Sterility

4 , 9 ~ lii ad Days of the luteal phase related to the LH peak ( day 0 ) Figure 1 Relationship between 28 endometrial biopsies dated according to morphometric methods and cycle days (as related to the LH surge 0 on which the biopsies were taken). significant correlations between the histologic dating of the endometrium and the LH surge, it was felt that the day of the LH surge should be used as a point of reference for ovulation. However, taking into account that the histologic dating of the CL could not be done on a day-to-day basis but rather classified in four stages of development during the postovulatory phase, the clinical material was divided into four arbitrarily chosen groups; the first one included the biopsies obtained between days LH 0 and LH +3, the second one comprised biopsies taken between days LH+4 and LH+7, the third one included material obtained between days LH +8 and LH + 11, and the last group consisted of biopsies taken between days LH + 12 and the day of the onset of menstruation. The data obtained from the morphometric analysis of the endometrial biopsies were then compared with the corresponding CL biopsy. (see Fig. 2a to h). As revealed in Figure 3, a highly significant correlation was found between the endometrial biopsies dated in relation to the LH surge and the histologic stages of the CL development (r = 0.918). The distribution of the histologic material from the 28 patients when divided into the four groups is shown in Table 1. Group I, II, and IV each consisted of material from 6 women, whereas group III included material from 10 women. The mean values of some of the morphometric indices measured in the endometrial biopsies and arranged into the groups specified above are shown in Table 2. The number of glands per mm 2 did not significantly change during the luteal phase. How-. ever, the number of glandular mitoses per 1,000 glandular cells was significantly higher when the biopsies obtained during days LH 0 to LH +3 were compared with those obtained at LH+4 to LH+7 and at LH+8 to LH+11 (P < 0.01) as well as compared with those obtained after day LH + 12 (P < 0.05). A significant increase was found in the glandular diameter when endometrial biopsies obtained at days LH 0 to LH +3 were compared with those of days LH+4 to LH+7 (P < 0.05) and of days LH+8 to LH + 11 (P < 0.01). The height of the glandular epithelium significantly decreased when the material obtained at days LH 0 to LH+3 was compared with that of LH +8 to LH + 11 (P < 0.001) and days LH+12 to the onset of menstruation (P < 0.01). Basal vacuolization of the glandular epithelial cells was only observed during the first 6 days after ovulation. After day LH +6, no basal vacuoles were found. The epithelial height of the fallopian tube showed a significant decrease after day LH +3 (P < 0.01) when compared with days LH+4 to LH +7 and when compared with the two other groups of the luteal phase. The morphometric values of the endometrium and the fallopian tube were also compared with the plasma levels of E 2 and P on the day of the ~iopsy and with the steroid production of the CL after 24 hours' incubation. As indicated in Table 3, a significant negative correlation was found between the number of stromal mitoses of the endometrium and the circulating P levels at days LH +8 to LH The same index showed a positive correlation with the circulating E 2 values premenstrually. The size of the endometrial glands was positively correlated to the circulating levels of P at days LH +8 to LH A positive correlation was also found between the glandular epithelial height and the plasma P values at days LH+4 to LH+7, whereas the same index was negatively correlated to the E 2 values in plasma premenstrually. The number of glandular cells showing basal vacuoles was positively correlated to the circulating P values of day LH +4 to LH+7. Very few significant correlations were found between the endometrial indices and the steroid production in vitro of the CL at various stages of the postovulatory phase. The glandular diameter was positively correlated to the production of E 2 in the early postovulatory phase (LH 0 to LH +3) and positively correlated to the P production during the period of days LH +8 to LH The number of glandular cells showing basal vacuolization was posi- Vol. 56, No. 5, November 1991 Kim-Bjorklund et al. Compare endometriumfcl function 845

5 Figure 2 This figure shows the histologic structure of the endometrium and the CL in the same woman as obtained from four patients representing stage 1 (a), stage 2 (c), stage 3 (e), and stage 4 (g) of the CL development. The histologic changes are described in detail in the text (see Materials and Methods). Corresponding endometrial biopsies are shown in b, d, f, and h. Note the lack of basal vacuoles in b, the presence of basal vacuoles in the glandular cells in d, the secretory changes and dilatation of the glands in f, and the regressive changes in h were 420X. 846 Kim-Bjorklund et al. Compare endometriumfcl function Fertility and Sterility

6 5 4 d ol---~--~---l---l--_j--~l---l---~--~ -2 o ro ~ u ~ Endometrial dates Figure 3 Relationship between endometrial dating and the histologic stages of CL development when grouped in relation to the LH surge 0. tively correlated to the E 2 produced by the CL in the early postovulatory phase (LH 0 to LH+3). As to the morphological changes of the fallopian tube, a positive correlation was found between the height of the epithelium and the plasma levels of E 2 in the early postovulatory phase (LH 0 to LH+3). A positive correlation was also found between the tubal epithelial height and the E 2 produced by the CL in the period LH+4 to LH+7. DISCUSSION The results of the present study have shown a highly significant correlation between the endometrial dating and the dating of the CL, when grouped in relation to the LH surge. Taking into account that the CL is responsible for the production of E 2 and P during the postovulatory phase, one would expect a similar correlation between the endometrial changes and the circulating levels of E 2 and P. However, during the early phase of the CL development (LH O/LH+3), no significant correlation was found between the plasma levels of E 2 and P and any morphometric indices measured in the endometrium. When the morphometric indices were correlated to the CL production of E 2 and P in vitro, a positive correlation was found between the E 2 produced and two morphometric indices: the glandular diameter and the number of vacuolated cells. Both these indices have previously been reported to be correlated to the plasma P values. 2 However, one of the indices (the glandular diameter) was previously found to be significantly correlated to the plasma E 2 levels during the preovulatory phase. 2 The positive correlation observed between the E 2 produced in vitro by the CL obtained during the 1st 3 days after ovulation and the number of vacuolated glandular cells of the endometrium is surprising. The presence of basal vacuolation in the glandular epithelium has usually been considered as significant for a P effect.l-4 17 It is noteworthy that already in 1965, Pincus18 referred to the development of basal vacuoles in the endometrial glandular cells in rabbits as a sensitive test of progestational activity of various steroids. The positive correlation found between the E 2 produced by the early stage CL in vitro and the number of vacuolated glandular cells of the endometrium observed in the present study, therefore, has to be seen in a broader perspective, for instance, taking into account the need of E 2 production to produce an appropriate amount of P receptors. 7 The positive correlation between the plasma P values Table 1 Dating of the Endometrium and CL in Relation to the LH Surge (day = 0) During the Postovulatory Phase in Normally Menstruating Women LH OtoLH+3 LH+4toLH+7 LH+S to LH+ll LH + 12 to menstruation Endometrium CL" Endometrium CL" Endometrium CL" Endometrium CL" b LH+2 - LH+4 2 LH+9 3 LH+13 4 LH+1/+2 1 LH+6 2 LH+9 3 LH+ll 3 Late proliferation 1 LH+7 2 LH+S 3 LH+12 3 LH+l/+2 1 LH+5 3 LH+S 3 LH+12 3 LH+3 1 LH+7 2 LH+9 3 Premenstrual 4 LH+2 1 LH+4/+5 2 LH+9 3 LH+13 3to4 LH+S 3 LH+S 3 LH+9 3 LH+lO 3 Stages 1, 2, 3, and 4 according to classification of the CL. Vol. 56, No.5, November 1991 b Insufficient material. Kim-Bjorklund et al. Compare endometrium/cl function 847

7 Table 2 Morphometric Analysis of Various Indices of the Endometrium and the Fallopian Tube in the Four Groups Related to LH Peak Morphometric index Endometrium No. of glands/mm 2 Glandular mitoses/1,000 cells Stromal mitoses/1,000 cells Glandular diameter (~tm) Glandular epithelial height (~tm) No. of vacuolated cells/1,000 glandular cells Fallopian tube Epithelial height (JLm) LHOto LH ± ± ± ± ± ± ± 2.4 LH+4 to LH+8 to LH+12 to LH+7 LH+ll menstruation 20.4 ± ± ± ± 0.4a oa ob 0.3 ± ± ± ± 20.0b 73.5 ± 18.3a 58.8 ± ± ± 1. 7' d 17.0 ± 2.1 a 223 ± 393 o o 16.1 ± 3.4a 16.3 ± 2.3a 15.9 ± 3.1 a a P < 0.01 when compared with group LH+O/LH+3. b P < 0.05 when compared with group LH+O/LH+3. 'P < when compared with group LH+O/LH+3. d P < 0.01 when compared with group LH+4/LH+7. P < 0.05 when compared with group LH+4/LH+7. and the number of subnuclear vacuolated glandular cells found in the present study during the period LH+4/LH+7 confirms, however, previous findings.1 2 However, it must be remembered that the development of the CL is a dynamic process that induces a similar dynamic process in the steroid hormones' target organs. Plasma steroid samples taken occasionally during the luteal phase are likely to be of limited value for evaluating the CL activity. In general, it can therefore be concluded that the development of the initial secretory changes in the endometrial tissue during the early postovulatory phase may be more related to the concentration of Preceptors (or other nonidentified factors) than to the plasma concentration of P and E Another correlation of importance during the postovulatory phase is the one between the plasma P values and the size of the glands. In the present study, this correlation was not found until the period LH +8 to LH + 11, at the time when the in vitro CL production of P also was positively correlated to the glandular diameter. This finding is in agreement with previous correlation studies in which the postovulatory dilatation of the glands has been postulated to reflect a synergistic influence of the E2 on the glands during the preovulatory phase and the P produced by the CL during the postovulatory phase.2 3 It is noteworthy that the strong positive correlation between the size of the glands and the plasma P values during the period LH +8/LH + 11 was observed when the CL had reached its maturity stage. The findings of the present study suggest a latency of the endometrium to respond to the P at maximal stimulation in a maximal way. The dilatation of the glands observed at day LH +8/LH + 11 may therefore reflect the influence of the P production of the CL for the total period of 8 or 11 days after the ovulation. A disturbed CL function with a deficient P production may be accompanied by an insufficient dilatation of the glandular lumen. This hypothesis remains however to be further investigated. The results of the present study do not provide any evidence that persisting basal vacuolization should be a significant morphological sign of CL deficiency. Several studies postulating this hypothesis have been relying their morphological data on the conventional criteria set by Noyes et al.17 Sometimes the dating has been assigned retrospectively from the onset of the next menstrual period It is, however, now well established that the postovulatory phase varies considerably in length The use of the onset of the next menstrual period as guide for dating the endometrium is therefore likely to introduce an incorrect variability. Furthermore, objective morphometric analysis of endometrial biopsies have been proven by blinded prospective studies to be superior to the more subjective evaluation represented by the classical dating The regression of the CL is followed by decreasing plasma levels of P and a decrease in the steroid synthesis of the CL when studied in vitro. It is noteworthy that in the regression phase of the CL, a strong positive correlation was found between the plasma E2 levels and the number of stromal mitoses, suggesting that the inhibitory influence of P on the mitotic activity had diminished. This observation is also supported by previous reports on the P receptors indicating the gradual disappearance in its concentration during the late secretory phase. 7 From the results of the present study, it may be concluded that when related to the LH surge the 848 Kim-Bjorklund et al. Compare endometrium/cl function Fertility and Sterility

8 Table 3 Correlation Coefficients Between E2 and P Levels Produced by the CL and E2 and P Levels in Peripheral Plasma Versus Morphometric Indices of the Endometrium and Fallopian Tube Days of luteal phase LH±Oto LH+3 CL Morphometric index E2 p E2 Plasma LH±4to LH±7 CL Plasma p E2 p E2 p Endometrium No. glands Mitoses glandular Mitoses stromal Diameter glandular 0.84" Epithelial height Vacuolated cells 0.85" Fallopian tube Epithelial height " LH±8 to LH±ll " b " LH±12 to menstruation CL Morphometric index E2 p E2 Endometrium No. glands Mitoses glandular Mitoses stromal Diameter glandular " 0.14 Epithelial height Vacuolated cells Fallopian tube Epithelial height a P < Plasma CL Plasma p E2 p E2 p " " b " b p < CL undergoes histologic changes corresponding to maturation and regression during the postovulatory phase. These histologic changes permit an approximate dating of the CL. The endometrium reacts with a number of specific histologic changes particularly during the first 6 days after ovulation at the time when the dating of the uterine mucosa could be carried out with a reasonably high precision. The size of the endometrial glands is positively correlated to the circulating levels of P with a high degree of significance (P < 0.01) during the period LH+8/ LH It is likely that a significant relationship exists between a fully developed CL producing plasma levels of P at a level of 16 nmol/l or more for a minimum of 5 days and some specific morphological changes of the endometrium such as the dilatation of the glands. An endometrial biopsy timed in relation to the LH surge may therefore be useful in assessing the CL function at least in normally menstruating women. In the present study, the epithelium of the fallopian tube was found to be significantly influenced by the steroids produced by the CL during the postovulatory phase. A positive correlation was found between the epithelium height and the plasma E 2 values during the early postovulatory phase and between the E 2 produced by the CL in vitro in the period LH+4 to LH+7. These findings open some new venues in the field of the morphology of the fallopian tube. It is well known that the epithelium of the fallopian tube is composed of ciliated and nonciliated cells In scanning electron microscopic studies, it has been shown that the tubal epithelium undergoes some cyclic changes mainly in the nonciliated cells. 24 Administration of ethinyl E 2 to fertile and postmenopausal women has also been reported to stimulate the growth of the ciliated cells. 25 In the present study, only the height of the tubal epithelium and the interstitial edema were the indices measured. The ciliated cells could not be assessed in the techniques used aimed at light microscopic examination. Nevertheless, the correlation analyses of the present study confirm the importance of E 2 as a stimulating Vol. 56, No. 5, November 1991 Kim-Bjorklund et al. Compare endometrium/cl function 849

9 factor of the epithelial development. It is most likely that the tubal physiology is influenced by the ovarian hormones and that the mechanism of the ovum transport is depending on the interaction between the steroids produced by the CL and the morphology of the fallopian tubes. This interaction, however, remains to be further studied. Ackrwwledgments. The expert technical assistance of Mrs. Astrid Haggblad and Mrs. Margot Carlsson, Stockholm, as well as of Mrs. Erika Jakobsson-Strom and Mrs. Myriam McNeill, Geneva, is gratefully acknowledged. REFERENCES 1. Li TC, Rogers A W, Dockery P, Lenton EA, Cooke ID: A new method of histologic dating of human endometrium in the luteal phase. Fertil Steril 50:52, Johannisson E, Parker RA, Landgren B-M, Diczfalusy E: Morphometric analysis of the human endometrium in relation to peripheral hormone levels. Fertil Steril 38:564, Johannisson E, Landgren B-M, Rohr HP, Diczfalusy E: Endometrial morphology and peripheral hormone levels in women with regular menstrual cycles. Fertil Steril 48:401, Cooke ID, Rao ChV, Yussman MA: Plasma gonadotrophin and sex steroid hormone level during early, mid follicular and luteal phases of women with luteal phase defects. Fertil Steril 40:45, Cumming DC, Honore LH, Scott JZ, Williams KP: The late luteal phase in infertile women: comparison of simultaneous endometrial biopsy and progesterone levels. Fertil Steril 43: 715, Wentz AC: Endometrial biopsy in the evaluation of infertility. Fertil Steril 33:121, Gravanis A, Zorn J-R, Tanguy G, Nessman C, Cedard L, Robel P: The disharmonic luteal phase syndrome: endometrial progesterone receptor and endometrial dehydrogenase. Fertil Steril 42:730, McRae MA, Blasco L, Lytte CR: Serum hormones and their receptors in women with normal and inadequate corpus luteum function. Fertil Steril 42:58, Laatikainen T, Anderson B, Karkkainen J, Wahlstrom T: Progestin receptor levels in endometria with delayed or incomplete secretory changes. Obstet Gynecol 62:592, Kim Bjorklund T, Landgren B-M, Hamberger L: In vitro synthesis of steroid hormones in corpora lutea from normal women and women treated with 300 p.g norethisterone. J Clin Endocrinol Metab. In press 11. Comer GW, Jr: The histological dating of the human corpus luteum of menstruation. Am J Anat 98:377, Novak E, Woodruff JD: Gynecology and Obstetric Pathology, 7th edition. Philadelphia, W. B. Saunders Corp., 1979, p Aso T, Guerrero R, Cekan SZ, Diczfalusy E: A rapid 5-hour radioimmunoassay of progesterone and oestradiol in human plasma. Clin Endocrinol (OxO 4:173, Sufi SB, Donaldson A, Jeffcoate SL: Method Manual, WHO Programme for the Provision of Matched Assay Reagent, loth edition. World Health Organization, Geneva, Switzerland, Snedecor G, Cochran WG: Statistical methods, 6th edition. Ames, Iowa, The Iowa State University Press, 1972, p Gaddum JH: Lognormal distribution. Nature 156:163, Noyes RW, Hertig AT, Rock J: Dating the endometrial biopsy. Fertil Steril 1:3, Pincus G: The control of fertility. New York, Academic Press, 1965, p Gautay JP, de Brux J, Tajchner G, Robel P, Mouren M: Clinical investigation of the menstrual cycle III. Clinical, endometrial and endocrine aspects of the luteal defect. Fertil Steril 35:296, Cooke ID, Morgan CA, Parry TE: Correlation of endometrial biopsy and plasma progesterone levels in infertile women. J Obstet Gynecol Br Commonw 76:647, Lenton EA, Landgren B-M, Sexton L: Normal variation in the length of the luteal phase of the menstrual cycle: identification of the short luteal phase. Br J Obstet Gynecol 91: 685, Li TC, Rogers A, Lenton E, Dockery P, Cooke I: A comparison between two methods of chronological dating of human endometrial biopsies during the luteal phase, and their correlation with histologic dating. Fertil Steril 48:928, Li TC, Dockery P, Rogers A, Cooke 1: How precise is histologic dating of endometrium using standard dating criteria? Fertil Steril 51:759, Verhage HG, Bareither ML, Jaffe RC, Akbar M: Cyclic changes in ciliation, secretion and cell height of the oviductal epithelium in women. Am J Anat 156:505, Patek E, Nilsson L, Johannisson E, Hellema M, Bout J: Scanning electron microscopic study of the human fallopian tube: report III. The effect of mid pregnancy and various steroids. Fertil Steril 24:31, Kim-Bjorklund et al. Compare endometrium/cl functwn Fertility and Sterility