Initial Preoperative Hemoglobin Level Affects the Rate of Decline in Anti-Müllerian Hormone Levels after Laparoscopic Ovarian Cystectomy in Women with Ovarian Endometriosis

Ovarian reserve, defined as the pool of oocytes within the ovaries that are available for ovulation, stands as a critical factor that significantly impacts the female reproductive potential [ 1 ]. Diminished ovarian reserve (DOR) can have profound implications for fertility and family planning [ 2 ]. Premature ovarian insufficiency (POI), characterized by elevated gonadotropins, low estrogen, and menstrual disturbances such as amenorrhea or oligomenorrhea, denotes the loss of ovarian activity before the age of 40 [ 3 ]. Notably, alongside its effects on female fertility, POI carries a substantial lifetime risk of cardiovascular disease, reduction in bone density, neurocognitive disorders and psychological distress, and vasomotor symptoms, collectively leading to decreased overall quality of life [ 4 ]. Thus, it is pertinent to recognize that DOR not only poses a significant concern for fertility but also has implications for long-term health outcomes. A variety of factors, including age, environmental factors such as smoking, gynecologic diseases such as endometriosis and polycystic ovary syndrome, and iatrogenic factors such as chemotherapy, radiation therapy, and especially ovarian surgery, are widely acknowledged to influence ovarian reserve [ 1 5 ]. Laparoscopic ovarian cystectomy (LOC) stands as a minimally invasive surgical procedure necessary for pain relief and the prevention of complications in patients with benign ovarian cysts such as ovarian endometriotic cysts. However, LOC has been identified as a cause of unavoidable reduction in ovarian reserve [ 6 7 8 9 10 11 12 ]. The histologic diagnosis of cysts [ 8 13 14 15 ] and the difference between unilateral and bilateral cystectomy [ 7 9 ] have emerged as crucial factors linked to the postoperative reduction in ovarian reserve after ovarian cystectomy [ 7 9 13 14 15 ]. Our previous study was conducted to examine the early postoperative decline in serum anti-Müllerian hormone (AMH) levels following unilateral LOC among patients categorized by histologic diagnosis [ 8 ]. It revealed a higher rate of AMH decline after LOC in cases of endometriomas and teratomas in comparison to other benign cysts. Other studies have also reported a greater reduction in ovarian reserve after ovarian cystectomy in patients with ovarian endometrioma than in patients with non-endometriotic cysts [ 13 14 15 ]. Hirokawa et al. [ 9 ] demonstrated that performing a bilateral cystectomy for endometriomas leads to a significant reduction in serum AMH levels, whereas a unilateral cystectomy maintains AMH levels comparable to those observed before surgery. However, except for the histology of cysts and bilaterality, research exploring other clinical and surgical characteristics affecting ovarian reserve after LOC remains limited, with existing studies often presenting conflicting results [ 6 7 8 9 10 11 12 ], highlighting the necessity for further investigations. In addition to the histological diagnosis of cysts and the difference between unilateral versus bilateral cystectomy, this study aimed to investigate what other factors influence the decline in ovarian reserve following laparoscopic ovarian surgery.

A total of 22 patients were included in this study. The clinical characteristics of the subjects who participated in this study are shown in Table 1 . Table 2 shows the results of analyzing the correlation between clinical parameters related to laparoscopic ovarian surgery and changes in AMH levels after surgery. The preoperative hemoglobin level, preoperative white blood cell count, and preoperative AMH concentration were the parameters related to absolute changes in AMH level after surgery. Among these parameters, only the preoperative hemoglobin level was correlated with the rate of decline in the AMH level after LOC ( Table 2 and Fig. 1 ). The preoperative serum AMH concentration was correlated with the amount of postoperative AMH change but not with the rate of decline in the AMH level after LOC. Study participants were divided into two groups according to the approximate mean value of preoperative hemoglobin level of 13.0 g/dL. Among the patients whose preoperative hemoglobin level was 13.0 g/dL or higher, 8 patients had a prominent decrease in their AMH levels by 35% or more after surgery (8/13) ( Fig. 1 ). On the other hand, among the patients with a preoperative hemoglobin level less than 13.0 g/dL, there was no patient with a decrease in AMH by more than 35% after surgery (0/9, P = 0.006). There was no significant difference in AMH levels between the two groups ( P = 0.393).

This study aimed to explore the factors contributing to the decline in ovarian reserve following ovarian cystectomy. Histological differences in ovarian cysts and the difference between unilateral versus bilateral cystectomy have been proven to be factors affecting the reduction in ovarian reserve after surgery [ 7 8 9 13 14 15 16 17 ]. However, in addition to the above 2 factors, previous studies on the factors affecting ovarian reserve following ovarian cystectomy remain relatively limited and have yielded conflicting results, thus accentuating the imperative for further comprehensive study [ 6 7 8 9 10 11 12 ]. Therefore, to identify other factors affecting the decrease in ovarian reserve after ovarian surgery besides the above 2 factors of cyst histology and bilaterality, this study was conducted only in patients who underwent unilateral LOC for ovarian endometriosis without other ovarian pathologies, and the results show that only the preoperative initial hemoglobin level exhibited a significant correlation with the rate of decline in the AMH level after LOC in women with endometriosis. LOC is recommended as a classical surgical approach for managing benign ovarian cysts [ 18 ]. However, apprehensions have arisen concerning the safety of cystectomy due to the inherent risk of inadvertently compromising normal ovarian tissue, even when performed by skilled practitioners [ 19 ]. Various diagnostic tests, such as measurements of follicle-stimulating hormone, estradiol, the antral follicle count (AFC), and AMH, have been utilized to assess ovarian reserve, thereby evaluating the potential impact of surgery on the residual normal ovarian cortex. Serum AMH levels, in particular, hold substantial significance, as they strongly reflect the potential pool of ovulatory follicles [ 20 21 ]. In the present study, the initial preoperative AMH level showed a positive correlation with the amount of AMH reduction after LOC ( r = 0.793, P < 0.001), but it was not significantly correlated with the rate of decline in AMH levels after LOC ( P = 0.165). To our knowledge, our study is the first to evaluate the relationship between the initial AMH level and the absolute reduction in the AMH level after LOC. Ozaki et al. [ 22 ] found a negative correlation between preoperative serum AMH levels and postoperative adverse DOR (aDOR), defined as a decrease in AMH concentrations to < 1.1 ng/mL after ovarian cystectomy in their study. The initial AMH level was a significant determinant impacting the likelihood of a patient experiencing postoperative aDOR at 3 and 6 months after surgery. In contrast to our findings, a few studies have demonstrated positive correlations between the initial AMH level and the rate of decline in AMH levels after ovarian surgery. Celik et al. [ 6 ] reported that the initial AMH level was the only factor positively correlated with the rate of decline in postoperative AMH levels. Another study [ 12 ] also noted a positive correlation between the rate of decline in the AMH level and the initial AMH level. However, in both studies, no correlations were established between the preoperative serum AMH level and AFC. Considering the close association between AMH and AFC, along with the prevalent use of AMH as a surrogate marker for AFC [ 20 ], the discordance in AFC and AMH measurements in these 2 studies may raise considerations regarding their validity. In our study, cyst size was not demonstrated to have any impact on the decline in AMH levels after LOC. Our findings align with other studies, such as that conducted by Hirokawa et al. [ 9 ], who found no significant correlation between cyst diameters and the rates of decline in the serum AMH levels, as well as the studies by Uncu et al. [ 12 ] and Celik et al. [ 6 ]. In contrast, Chen et al. [ 7 ] found that the reduction rate of AMH was significantly higher in endometriomas larger than 7 cm in diameter than in those smaller than 7 cm. Additionally, Mircea et al. [ 23 ] reported that the removal of endometriomas larger than 5 cm could potentially cause substantial damage to ovarian reserve due to unclear boundaries between the endometrioma and surrounding ovarian tissue. They explained that because the larger the size of the endometrioma is, the wider the area of contact with normal ovarian tissue, the size of the endometrioma could affect the rate of AMH decline. However, it seems that these outcomes may vary depending on the expertise of the surgeon. In our study, age was not associated with the rate of decline in AMH after LOC, which is consistent with the results of previous studies [ 7 9 12 24 ]. Chen et al. [ 7 ] reported that while a patient’s age shows a statistically significant correlation with preoperative AMH levels, it was not associated with the rate of postoperative AMH decline. To the best of our knowledge, no study reported to date has evaluated whether preoperative hemoglobin levels and postoperative hemoglobin changes affect the decrease in ovarian reserve caused by ovarian surgery. In our study, we found a significant positive correlation between initial hemoglobin levels and both the absolute amount and the rate of decline in AMH levels after LOC for unilateral endometrioma. In particular, all of the patients with a notable AMH decline rate of 35% or more after LOC were found to be those whose initial hemoglobin level was 13.0 g/dL or higher. Exploring this cause-and-effect relationship presents challenges. One plausible hypothesis is that oxidative stress could contribute to the decline in ovarian reserve following laparoscopic surgery. First, oxidative stress is characterized by an imbalance between the production of reactive oxygen species (ROS) and their detoxification ability. Increased ROS production due to environmental stressors and xenobiotics can lead to oxidative stress and tissue damage [ 25 ]. Ovarian aging involves complex mechanisms, and oxidative stress is considered a significant contributor. Oxidative stress accelerates ovarian aging by promoting apoptosis, inflammation, mitochondrial damage, telomere shortening, and biomacromolecular damage [ 26 ]. Hemoglobin, the main cytosolic protein of red blood cells (RBCs), plays a pivotal role in initiating oxidative stress within RBCs [ 27 ]. Prolonged exposure of RBCs to thermal damage from the electrode device used during surgery can increase free radicals and oxidative stress. Consequently, increased ROS production and oxidative stress within ovaries with higher hemoglobin levels could potentially lead to damage to ovarian follicles and a subsequent decline in AMH secretion. Thermal stress is known to significantly reduce protective enzymes that guard against oxidative stress [ 28 ]. Moreover, despite the efficiency of bipolar coagulation as a time-saving surgical technique, the resulting thermal damage can be detrimental to ovarian stromal blood vessels and the ovarian parenchyma [ 29 ]. Song et al. [ 30 ] reported that, compared to bipolar coagulation, suturing resulted in a lower rate of decline in postoperative AMH. Similarly, Ding et al. [ 29 ] found that using sutures for hemostasis had a more beneficial impact than bipolar electrocoagulation had on ovarian reserve . In our study, coagulations using bipolar forceps were performed for hemostasis. Findings from previous studies that electrothermal coagulation has a worse effect on ovarian reserve than classical hemostasis by suturing partially support our hypothesis of hemoglobin-mediated ovarian tissue damage associated with these electrothermal devices. In this study, the CBC test included in the routine preoperative check-up tests performed on our study participants was not a standard CBC tests including differential cell count, but a routine CBC test without differential cell count. Therefore, we could not conduct the correlation analysis between the rate of decline in AMH levels and the well-known combined hematologic parameters such as neutrophil-lymphocyte ratio in this study. A question might arise as to whether it is appropriate to measure AMH levels 3 days after surgery for the purpose of assessing the changes in ovarian reserve after surgery. Griesinger et al. [ 31 ], however, found that serum AMH levels dropped to the minimum detection limit of 0.08 ng/mL within 84 hours post-surgery in premenopausal women undergoing bilateral salpingo-oophorectomy. Importantly, AMH elimination reached 84% within 3 days in most cases, implying practical implications for short-term AMH changes in research and clinical settings. These results support our study in which AMH levels were measured at 3 days postoperatively to evaluate AMH changes for assessing the impact of LOC on ovarian reserve. The main limitations of this study were the small sample size (n = 22) and the short-term study duration. Another important drawback of this study is that it was not possible to evaluate the association between the revised American Society of Reproductive Medicine (rASRM) score, which represents the severity of endometriosis, and the decline in ovarian reserve after LOC in this study. When reviewing the surgical records of the participants in this study, we found that the rASRM score was not properly reported in more than half of the patients. In conclusion, our results suggest that preoperative hemoglobin levels may be related to the rate of decline in AMH levels after LOC in the early postoperative period. However, this result was, in fact, unexpected in general, and the sample size of our study is too small to validate our study. In addition, it remains to be ascertained whether the effect of the initial hemoglobin level on the decline in AMH levels in the early postoperative period can lead to a long-term reduction in ovarian reserve after surgery. Therefore, further larger, multicenter prospective studies with long-term follow-ups will be needed to demonstrate the validity of our preliminary findings.

This study was performed on patients who underwent unilateral LOC and were diagnosed with ovarian endometriosis at Inje University Haeundae Paik Hospital from March 2011 to December 2013. Among the subjects between the ages of 25 and 45, only those with regular menstrual cycles between 21 and 35 days were included in the study. The criteria for exclusion from the study were as follows [ 8 16 ]: 1) history of previous uterine or adnexal surgery for gynecologic disease except for cesarean section, 2) cases of bilateral ovarian cystectomy for endometriosis, 3) cases of accompanying gynecological lesions other than endometriosis, and 4) history of taking any medication known to affect ovarian function within 6 months prior to surgery (e.g. oral contraceptives, other estrogen-progestogen therapy, glucocorticoids, anti-diabetic drugs, etc.). Patients who received a blood transfusion to correct anemia before surgery and those who received antibiotic treatment for infection or inflammation within 1 week before surgery were also excluded from this study. Information on the blood test results (including complete blood counts [CBC] and cancer antigen 125 levels) of the study participants before and after surgery and the clinical variables related to surgery were obtained through a thorough medical record review. In the present study, Δ means the postoperative blood level changes compared to the preoperative ones. For example, the Δ hemoglobin value was determined by subtracting the hemoglobin level on the first day after surgery from the preoperative hemoglobin level. In this study, the surgery time was defined as the period from the first surgical incision to the completion of the last suture of the incision site after surgery, and the diameter of the ovarian cyst was determined as the largest diameter of the ovarian cyst by ultrasound. This study was approved by the Institutional Review Board (IRB) of Inje University Haeundae Paik Hospital (IRB No. 129792-2014-091) [ 8 16 ], and the IRB waived the requirement for patient consent in this study. All unilateral LOCs were performed as follows [ 8 ]. An 11-mm trocar was inserted just below the umbilicus, then a 5-mm auxiliary trocar was inserted in the left lower abdomen, and another into the suprapubic area. Ovarian cyst resection was performed mainly using a monopolar scissor, and after the cyst was excised, hemostasis was attempted using minimal bipolar forceps. All surgeries were performed by the same surgeon highly skilled in minimally invasive gynecological surgery. Blood samples were collected before surgery and on the third day after surgery to determine the serum AMH levels from all study participants following the guidelines of the Declaration of Helsinki. The serum AMH level was measured using a commercially available enzyme-linked immunosorbent assay kit (AMH Gen II assay; Beckman Coulter, Inc.), and the lowest detection limit of the kit was 0.08 ng/mL with both the intra- and interassay coefficients of variation below 8.0% [ 8 16 ]. The rate of decline in AMH levels was calculated using the following formula [ 8 16 ]: (preoperative AMH level – postoperative Day 3 AMH level)/(preoperative AMH levels) × 100 (%). All values are expressed as the mean ± standard deviation. Pearson’s correlation coefficients and linear regression analysis were used to identify the factors related to the changes in the AMH level after surgery. A Mann-Whitney U test was used to compare the parameters between the two groups categorized according to preoperative hemoglobin level, and comparisons of the proportion of patients with a notable decrease in their AMH levels after surgery between the two groups were performed using a Fisher’s exact test. All statistical analyzes were performed using SPSS version 25.0 (IBM Co.), and P values of less than 0.05 were determined to indicate statistical significance.