Altered uterine artery blood flow impedance after danazol therapy: possible mode of action in dysfunctional uterine bleeding

Transcription

1 FERTILITY AND STERILITY VOL. 72, NO. 1, JULY 1999 Copyright 1999 American Society for Reproductive Medicine Published by Elsevier Science Inc. Printed on acid-free paper in U.S.A. Altered uterine artery blood flow impedance after danazol therapy: possible mode of action in dysfunctional uterine bleeding Jonathan Pepper, M.D., Paul J. Dewart, M.D., and Olufunso A. Oyesanya, M.D. Academic Department of Obstetrics and Gynaecology, University of Manchester, Manchester, England, United Kingdom Received September 11, 1998; revised and accepted February 10, Presented in abstract form at the 16th World Congress on Fertility and Sterility and the 54th Annual Meeting of the American Society for Reproductive Medicine, San Francisco, California, October 4 9, Reprint requests: Olufunso A. Oyesanya, M.D., Academic Department of Obstetrics and Gynaecology, University of Manchester, Research Floor, St. Mary s Hospital, Whitworth Park, Manchester M13 0JH, United Kingdom (FAX: ; /99/$20.00 PII S (99) Objective: To test the hypothesis that danazol increases the impedance to uterine circulation and hence reduces the effective uterine blood flow after a predetermined period of therapy. Design: Prospective, longitudinal study. Setting: Reproductive medicine unit of a university teaching hospital. Patient(s): Eight premenopausal women with dysfunctional uterine bleeding. Intervention(s): Six weeks of danazol therapy. Main Outcome Measure(s): The uterine artery blood flow impedance as indicated by the pulsatility and resistance indices; the hormonal profile (E 2, FSH, and LH levels); the uterine dimensions (length, width, anteroposterior diameter, and area); and the endometrial thickness. Result(s): The indices of uterine artery impedance were significantly increased after danazol therapy, indicating a possible reduction in the effective uterine artery blood flow. There was no statistically significant change in the hormonal profile, uterine dimensions, or endometrial thickness. Conclusion(s): Danazol therapy for 6 weeks results in a significant increase in the uterine artery impedance and hence a possible reduction in the effective uterine artery blood flow. This may explain in part its efficacy in the management of dysfunctional uterine bleeding and in the preoperative preparation of women undergoing endoscopic endometrial ablation. The exact mechanism for its action in this regard remains to be determined but appears to be independent of E 2 levels. This preliminary finding may help in monitoring the treatment of dysfunctional uterine bleeding, preoperative and postoperative investigation of women undergoing endoscopic endometrial ablation, and the development of alternative treatment strategies for dysfunctional uterine bleeding in the future. (Fertil Steril 1999;72: by American Society for Reproductive Medicine.) Key Words: DUB, menorrhagia, pelvic hemodynamics, pulsatility index, resistance index A perception of heavy menstrual bleeding (menorrhagia) was found in 31% of women in the United Kingdom in a recent national survey (1). Menorrhagia is a leading cause of morbidity in women (2), accounts for 12% of all specialist referrals (3), and is the main problem in more than 50% of women who undergo hysterectomy. In a substantial proportion of these cases, there is no clinical, endocrinologic, ultrasonographic, or histologic evidence of pelvic or other pathology, and the condition is called dysfunctional uterine bleeding (DUB). Because women with DUB have no demonstrable pathology, it is necessary to investigate possible etiologic mechanisms to develop reliable alternative, outpatient, nonoperative treatment strategies. This may reduce the morbidity of the condition, the substantial direct and indirect costs involved in its operative and nonoperative management, and other occupational, social, and economic consequences of DUB. Knowledge of the mode of action of current therapy for DUB is important for the development of methods for monitoring the response to such therapy and the development of alternative therapy. This knowledge also may be useful in the preoperative and postoperative inves- 66

2 tigation of women undergoing endoscopic endometrial ablation for DUB. It has been shown that danazol (an isoxal derivative of 17 -ethinyl testosterone) reduces menstrual blood loss (4, 5) and, therefore, it has become an established nonsurgical method of treating women with DUB. It also is used in the preoperative management of women with DUB before endoscopic endometrial electrodiathermy or laser ablation. Unfortunately, however, the exact method by which danazol reduces menstrual blood loss remains controversial (6 8). We therefore performed this prospective longitudinal study using color Doppler imaging (and concurrent hormone assays) to test the hypothesis that danazol increases the impedance to uterine circulation and hence reduces the effective uterine blood flow after a predetermined period of therapy. We are not aware of any previous prospective, longitudinal study of the effect of danazol on uterine blood flow impedance in women with DUB. MATERIALS AND METHODS This study was approved by the local research ethics committee. All volunteers gave prior informed consent. The study population consisted of eight regularly cycling, premenopausal women (mean [ SD] age, years) with at least one ovary. Each woman acted as her own control. It was a condition of recruitment that volunteers should be [1] 40 years of age; [2] of proven fertility; [3] not pregnant; and [4] identified as having DUB, without any ultrasonographic evidence of uterine, ovarian, or other pelvic pathology. Women with polycystic ovaries were excluded. Any volunteer who was pregnant or lactating, who had a history of pelvic disease or surgery, or who was taking concomitant hormonal or nonhormonal medication also was excluded from the study. All the volunteers were seen on day 3 of their menstrual cycle (the first day of bleeding being day 1). At this first (basal, pretreatment) visit, the volunteers clinical and biologic data were recorded, and blood sampling, transvaginal ultrasonography, and color Doppler imaging of the uterine blood flow were performed. Venipuncture was performed to collect blood samples for hormonal analysis. The samples were centrifuged (at a preset speed and time for all samples throughout the study [2,500 rpm for 15 minutes]), and the supernatant was frozen immediately at 20 C. All samples subsequently were assayed together as a batch to reduce the interassay variability. Our methods of transvaginal ultrasonography and color Doppler imaging have been described previously (9 11). All scans were performed by the same operator (J.P.) in the afternoon (between 1 PM and 3 PM) using the same ATL 5-MHz transvaginal probe and ATL HDI Ultramark 9 computerized sonographic imaging system (Advanced Technology Laboratories Inc., Bothell, WA). The intraobserver variability was 10% for all measurements. The maximum longitudinal diameter (in millimeters) measured from the internal os to the fundus and the maximum anteroposterior and mediolateral diameters of the uterus were used as indices of uterine size. The endometrial thickness (in millimeters) was measured in the longitudinal plane at the widest point across the cavity from the anterior to the posterior endometrial-myometrial interfaces. The Doppler gate was positioned on each uterine artery at a point just lateral to the internal os to detect the maximal signals, which then were displayed as flow velocity waveforms. These waveforms were analyzed online, using the ATL machine s built-in computerized algorithms to determine the peak Doppler-shifted frequency (A), the minimum Doppler-shifted frequency (B), and the mean Dopplershifted frequency over the cardiac cycle (mean). The impedance to blood flow was expressed as the pulsatility index and the resistance index. These were calculated electronically using the ATL machine s built-in computerized algorithms according to the following established formulas: Pulsatility index (A B)/mean (1) Resistance index (A B)/A (2) There was no statistically significant difference between the left and right uterine artery impedance indices. Consequently, the mean left and right impedance values were used for the analysis. The serum E 2 assay was performed with the use of a no-extraction, solid-phase iodine-125 RIA in a commercially available kit (Coat-a-Count; Diagnostic Products Corporation, Los Angeles, CA). The intra-assay coefficient of variation was 4% 7%. Serum LH and FSH levels were determined with the use of microparticle quantitative enzyme immunoassays in commercially available kits (IM x System, Abbott Laboratories, Diagnostics Division, Abbott Park, IL). The intra-assay coefficients of variation were 3.1% 5.5% and 3.8% 4.4%, respectively. After transvaginal ultrasonography, color Doppler imaging, and collection of blood samples, danazol (200 mg three times daily for 6 weeks) was administered to each volunteer. However, for logistic reasons, the follow-up ultrasonography, color Doppler imaging, and venipuncture were performed on a particular day of the week (Thursday) at a particular time (afternoon). Thus, the duration of danazol therapy (in days) before the follow-up examination varied slightly from patient to patient; the mean ( SD) was days. Each continuous data set was assessed for normality and expressed as the mean SD. In view of the longitudinal nature of the experimental design with repeated measures of each characteristic, we performed a univariate analysis for each characteristic using paired t-tests to compare changes FERTILITY & STERILITY 67

3 TABLE 1 Uterine dimensions, endometrial thickness, and hormonal profiles of women with dysfunctional uterine bleeding before and after danazol therapy. Parameter Before danazol therapy (n 8) over time (i.e., before and after the predetermined period of danazol therapy). P.05 was considered statistically significant. RESULTS After danazol therapy (n 8) Uterine dimension Length (cm) Width (cm) AP (cm) Endometrial thickness (cm) Hormonal profile FSH level (IU/L) LH level (IU/L) E 2 level (pmol/l) Note: Data are means SD. All P values are not statistically significant. AP anteroposterior diameter of the uterus. All the volunteers completed the study. Table 1 illustrates the uterine dimensions, endometrial thickness, and hormonal profile before and after danazol therapy. There was no statistically significant difference between the uterine length, width, or anteroposterior diameter, or the endometrial thickness before and after treatment with danazol. There also was no significant change in the levels of E 2, FSH, and LH over the study period. Figure 1 illustrates the indices of uterine artery blood flow impedance before and after danazol therapy. After danazol therapy, there was a significant increase in both the pulsatility index and the resistance index, indicating a higher vascular impedance and consequently a possible reduction in the effective blood flow to the uterus. DISCUSSION The present study demonstrated an increase in the indices of uterine artery impedance and, consequently, a possible reduction of the effective uterine artery blood flow after a short course of danazol therapy. This finding may explain in part the effect of danazol in reducing menstrual blood loss in women with DUB. The reason for this observation is not clear. Danazol may exert a direct effect on the uterine arteries or a secondary effect on the endometrium, affecting the smaller resistance vessels (i.e., the subendometrial vessels) (12), leading to decreased blood flow. It has been suggested that danazol may reduce menstrual blood loss by rendering the endometrium atrophic (13). However, the effect of danazol on the thickness of the endometrium seems to be controversial given the contradictory results of previous studies (13 15). Although some studies suggested an alteration in endometrial thickness after danazol therapy (13), others did not (14). The present study did not find any statistically significant alteration in endometrial thickness after danazol therapy. Although the mean endometrial thickness was slightly lower after danazol therapy, the difference was not statistically significant. This finding may be a reflection of the small number of patients in the present study, but it also is possible that the longer periods of therapy that are commonly used in the clinical management of DUB may result in endometrial atrophy. One previous study (15) showed an overall significant FIGURE 1 Indices of uterine artery blood flow impedance before and after danazol therapy. 68 Pepper et al. Danazol and uterine blood flow impedance Vol. 72, No. 1, July 1999

4 reduction in endometrial thickness after pretreatment with danazol but a lower incidence of amenorrhea after endometrial laser ablation in younger women compared with older women. Thus, it is plausible that the absence of a reduction in endometrial thickness in our present study population may be due in part to the younger age of our study population ( years). Nevertheless, we believe that the absence of endometrial atrophy during this short period of therapy removes a potential confounding variable, despite our observations regarding uterine artery impedance. Previous studies have suggested that danazol reduces menstrual blood loss by reducing the circulating levels of E 2 (16). The present study did not show a statistically significant reduction in the levels of E 2 after 6 weeks of danazol therapy. Although the mean E 2 level was slightly lower after danazol therapy, the difference was not statistically significant. On the other hand, a previous study did not demonstrate any reduction in the E 2 levels after danazol therapy for 91 days (17). Other studies (8, 18, 19) have demonstrated that danazol does not bind to E 2 receptors. It previously was assumed that danazol alters E 2 levels through an effect on basal FSH and LH, but the present study did not demonstrate any significant reduction in FSH or LH levels after danazol therapy. This finding is in agreement with previous studies of premenopausal women that also failed to show significant reductions in basal FSH and LH levels after danazol therapy (20). The absence of a significant change in E 2 levels in our study population after a short period of danazol therapy may indicate that its initial effect on uterine vascular impedance is independent of E 2 levels. Danazol is an iso-oxazol derivative of 17 -ethinyl testosterone that has been shown to bind and translocate androgen receptors (8, 18, 19). It also displaces testosterone from sex hormone-binding globulin binding sites, reduces testosterone binding to sex hormone-binding globulin, and has some peripheral androgenic effects either directly or through its metabolites (18, 19, 21). It is therefore possible that although it has some peripheral androgenic effects, it also acts as a competitive antagonist to androgen receptors at other sites. There is preliminary evidence that androgens and insulinlike growth factor modulate the effects of vascular endothelial growth factor, an angiogenic cytokine known to be involved in the rapid neoangiogenesis that accompanies the development of the corpus luteum and the cyclic regeneration of the endometrium (endometrial/subendometrial neoangiogenesis) (22). Competitive antagonism of this androgenic effect could interfere with endometrial vascular endothelial growth factor mediated neoangiogenesis and hence increase downstream impedance to uterine artery blood flow. It has been suggested that danazol exerts a suppressive effect on the corpus luteum (23) and the production of local growth factors (24). This also may lead to a reduction in the production of, or the effects of, vascular endothelial growth factor or other relevant local paracrine or autocrine angiogenic or growth factors involved in endometrial neoangiogenesis. However, this needs to be evaluated in larger prospective studies. We suggest that a previously undescribed mode of action of danazol is to decrease the blood flow through the uterus and that this effect could explain in part the benefit of danazol in the treatment of menorrhagia. In conclusion, the present study suggests that danazol therapy for 6 weeks causes a primary alteration in the uterine artery blood flow impedance (pulsatility index and resistance index) and, consequently, a possible reduction in the effective uterine artery blood flow. This observation may be responsible for secondary effects that have a therapeutic benefit in patients with DUB and in the preoperative preparation of women undergoing endometrial ablation. The exact mechanism for its action in this regard remains to be determined but appears to be independent of E 2 levels. Acknowledgments: The authors are grateful to Professor Henry C. Kitchener, M.D., and the entire staff of the Department of Obstetrics and Gynaecology, University of Manchester, and the South Manchester University Hospitals for their cooperation. References 1. MORI Women s health in Research study conducted on behalf of Parke-Davis Research Laboratories. 2. Hallberg L, Hogdahl AM, Nilsson L, Rybo G. Menstrual blood loss a population study. Acta Obstet Gynecol Scand 1966;45: Bradlow J, Coulter A, Brooks P. Patterns of referral. Oxford: Health Sciences Research Unit, Chimbira TH, Anderson AB, Naish C, Cope E, Turnbull AC. 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