Abstract
Purpose
To examine the pattern of kisspeptin expression throughout the menstrual cycle in polycystic ovary syndrome (PCOS) patients under the ovulation induction and identify any possible associations with early pregnancy.
Materials and methods
A prospective cohort of 80 PCOS women who expressed the desire for fertility was enrolled in this study. All of them received the ovulation induction by using letrozole. Levels of kisspeptin, luteinizing hormone (LH), and estradiol (E2) were measured at three different time points during menstruation. The early pregnancy rate was recorded for the study participants after three ovulation cycles.
Results
Kisspeptin levels varied regularly during the menstrual cycle, reaching a peak on the day of hCG injection and decreasing after ovulation. There was no significant correlation between kisspeptin and LH levels. Basal kisspeptin levels decreased after letrozole treatment without a significant difference while LH and E2 levels decreased significantly. PCOS participants who became pregnant early had higher basal kisspeptin levels compared to non-pregnant PCOS patients, which had a significant difference (P = 0.006). And the average basal kisspeptin level in pregnant patients was 2293.0 ± 398.7 pg/ml, with a 95% confidence interval of 1511.5–3074.5 pg/ml.
Conclusion
Kisspeptin levels in PCOS women undergoing ovulation induction showed a regular variation, which was similar with the healthy women reported in previous studies. The use of LE may result in PCOS endocrine improvement and fertility achievement. In a certain range, kisspeptin might be a potential predictor for early pregnancy in PCOS patients as people with slightly higher basal kisspeptin levels seemed more likely to be pregnant.
Keywords: Early pregnancy, Kisspeptin/KISS-1, Menstruation cycle, Ovulation induction, Polycystic ovarian syndrome
Introduction
Kisspeptins, a family of neuropeptides with arginine and phenylalanine at their C termini, serve as pivotal regulators of the mammalian reproductive axis, often known as the hypothalamic-pituitary-ovarian (HPO) in humans [1]. The KISS-receptor (KISS-R) is located in karyotype 19p13.3, and it is a G-protein-coupled receptor known as GPR54 [2]. The KISS-1 gene and its receptor exhibit widespread expression in numerous tissues and organs throughout the human body. This expression is not limited solely to the central nervous system, including regions such as the anteroventral periventricular or arcuate nucleus of the hypothalamus [3], but extends to peripheral tissues and organs, including the pancreas and ovaries [4]. Initially recognized as suppressors of metastasis in various tumor types, the kisspeptin/KISS-1R system has garnered increasing attention in recent years due to research affirming its pivotal role in human reproductive endocrinology. This system is intricately linked to the receptor of gonadotropin-releasing hormone (GnRH), thereby exerting regulatory control over women’s fertility.
Polycystic ovarian syndrome (PCOS) is a common endocrine disorder accompanied by menstrual irregularity and infertility. Numerous studies have indicated that PCOS entails a dysfunction of the hypothalamus-pituitary-ovary (HPO) axis and an endocrine disruption affecting gonadotropin-releasing hormone (GnRH). Letrozole (LE), belonging to the class of aromatase inhibitors, is used as the first-line drug in the ovulation induction treatment for PCOS [5]. Not only does it stimulate follicular growth, but it also suppresses hyperandrogenism [6].
Kisspeptin, functioning as a hypothalamic regulatory factor, exhibits regular expression patterns during the menstrual cycle in healthy women, as elucidated by Zai et al. [7]. Kisspeptin reaches its lowest level on the 3rd day of the period, then surges to its first peak again around day 11, when the dominant follicle (diameter ≥ 12 mm) appears. Subsequently, the level drops slightly and reaches its second peak on the day before ovulation, followed by a subsequent continuous decline. However, very little research has been conducted which focuses on the kisspeptin variation during menstruation in PCOS patients undergoing ovulation induction, as well as the relationship between kisspeptin and early pregnancy.
Therefore, in the context of ovulation induction with LE, our objective was to investigate the variation of plasma kisspeptin concentration during three distinct phases of the menstrual cycle in individuals with PCOS: basal, ovulatory, and luteal phases. Additionally, we compared the basal kisspeptin levels between PCOS women with pregnancy and non-pregnancy within 3 cycles of ovulation induction, trying to explore whether kisspeptin could be a predictor of early pregnancy and there was certain potential correlation between kisspeptin and early pregnancy in PCOS patients.
Materials and methods
Ethical approval and population
The Ethics Committee of Chongqing Medical University approved the study (approval number 2019-242) to undertake a prospective study of women with PCOS undergoing ovulation treatment from May 2020 to November 2021 in the Reproduction Medicine Center of the First Affiliated Hospital of Chongqing Medical University. Eighty women diagnosed with PCOS were ultimately included under the Rotterdam Standard (2003); details are as follows (2 out of 3): (1) oligo- and/or anovulation, (2) clinical and/or biochemical signs of hyperandrogenism, (3) and polycystic ovaries, and exclusion of other aetiologies (congenital adrenal hyperplasias, androgen-secreting tumors, Cushing’s syndrome) [8]. There were 102 women screened during the study, among whom 5 refused to join in and 17 did not meet the inclusion criteria. They were aged between 20 and 35 years old, with a BMI of 18.5–28.0 kg/m2, and had received no additional ovulation treatment in the last 3 months before participating in the research. Every patient in this study suffered menstrual disorder (cycle > 45 days), and some even had an irregular cycle which more than 90 days. Apart from that, there were several other exclusion criteria. Women with other infertility factors except PCOS, such as intrauterine lesions, ovarian lesions, fallopian tube diseases, and male factors, were excluded. Women diagnosed with endocrine dysfunction and other basic cardiovascular diseases like hypertension and heart attacks were also excluded. All participants gave their informed consent.
Study design
The therapeutic schedule was designed as shown in Fig. 1.
Fig. 1.
Process of the treatment
Description: *If necessary: On the 3rd after the LE use, there was no dominant follicle (diameter ≥ 12 mm) under the ultrasonography monitor
Ovulation-inducing treatment: Participants were administered LE (2.5 mg qd × 5 days) on the 5th to 9th day of the menstrual cycle. Three days after the medication, they returned and began using ultrasonography dynamically to monitor the follicular development and ovulation. At this time, if there was no dominant follicle (diameter ≥ 12 mm), the injection of Menotropin (HMG, 75 IU/bottle) was adopted as the single use of letrozole is not enough for ovulation induction and Menotropin can promote the follicle development just like the normal gonadotropin in the body. The injection of Menotropin continued until the day of human chorionic gonadotropin (hCG) administration when there were 1–2 follicles with a diameter greater than 18 mm in both ovaries. The participants were administered progesterone (100 mg/capsule) for 7 days as luteal support, using 1 softgel three times a day, 5 days after the hCG injection with 6000–10,000 IU.
Plasma samples: Blood was collected three times during the first cycle of induction at 9 a.m. consistently: stage 1 (the 3rd day of the menstrual cycle, the basal phase), stage 2 (the day of hCG injection), and stage 3 (the 5th day after hCG injection and before the progesterone taken, the luteal phases). If the participants did not get pregnant in the first cycle, they needed to contribute samples again at the basal phase.
Final therapy for different outcomes: Participants were required to check for pregnancy using pregnancy indicator papers after taking progesterone. Pregnancy status was continually monitored. In cases where pregnancy did not occur, the protocol involved waiting for the subsequent menstrual cycle and then recommencing the treatment. However, if follicular growth was inadequate or if there were more than three follicles exceeding 14 mm in size in both ovaries, the cycle was terminated. To mitigate the risk of ovarian hyperstimulation syndrome (OHSS) and multiple pregnancies, progesterone was recommended in such instances.
The research involved no more than three cycles. Women in any cycle whose serum hCG levels were greater than 5 mIU/ml within 2 weeks post-ovulation were clinically confirmed as pregnant upon the detection of a gestational sac and a heartbeat, typically observed 3–4 weeks later. Subsequently, these participants were followed up until the 11th week of gestation. Those who did not achieve pregnancy within three cycles were excluded from the study.
Plasma kisspeptin was detected using the enzyme-linked immunosorbent assay (ELISA) with the Kisspeptin-10/Measin (45–54)-Amide (Human) EIA Kit (EK-048-56, Phoenix Pharmaceuticals, Inc., Burlingame, CA, USA).
Statistical analyses
SPSS 22.0 for Windows (SPSS, IBM1, Chicago, IL) was used for all statistical calculations. Normal distribution data were statistically described in terms of mean ± standard deviation. Otherwise, the median method and quarters were used to calculate the skew distribution. The Shapiro–Wilk test was used to identify whether the data was in normal distribution. The indexes were compared using the independent sample t test and the rank-sum test. Pearson’s regression was used to estimate the relationship between related variables. P < 0.05 was considered statistically significant.
Results
Expression pattern of kisspeptin during menstruation in women with PCOS
Variations in the concentration of kisspeptin during the menstrual cycle in PCOS showed a regular pattern over time, with lower levels at stage 1 (2259.0 ± 680.1 pg/ml) and stage 3 (2294.5 ± 578.1 pg/ml) and the highest at stage 2 (2418.1 ± 648.2 pg/ml). The paired-samples t test revealed no statistical difference in pairwise comparisons among the three phases (P > 0.05, Fig. 2). Furthermore, the Pearson correlation analysis revealed that the levels of kisspeptin and luteinizing hormone (LH) were not significantly correlated at either stage 1 or stage 2, with a Pearson coefficient of − 0.375, P = 0.078, for the former and 0.221, P = 0.378, for the latter.
Fig. 2.
The expression of kisspeptin in the menstruation of PCOS patients under LE
Description: Stage 1 refers to the 3rd day, stage 2 refers to the day of hCG injection, and stage 3 refers to the 5th day after ovulation
Changes in hormonal levels after ovulation treatment
Changes in basal hormone levels in 64 women who failed to conceive in their first cycle were compared before and after ovulation induction. After the treatment of LE, although the basal kisspeptin level was slightly lower than before, there was no statistical difference (t = 1.03; P = 0.19). However, the basal LH and estradiol (E2) concentrations were significantly lower with 8.15 ± 3.94 vs. 11.83 ± 4.50 mIU/ml and 39.38 ± 13.21 vs. 53.81 ± 25.83 pg/ml respectively, which had statistical differences at P = 0.009 and P = 0.01 (Table 1).
Table 1.
The variation of the relative hormones at the basal level (3rd day)
| Hormone | Before treatment (N = 64) | After treatment (N = 64) | t | P |
|---|---|---|---|---|
| Kisspeptin (pg/ml) | 2506.4 ± 828.5 | 2327.1 ± 668.7 | 1.03 | 0.19 |
| LH (mIU/ml) | 11.83 ± 5.00 | 8.15 ± 3.94 | 2.06 | 0.009# |
| E2 (pg/ml) | 53.81 ± 25.83 | 39.38 ± 13.21 | 4.02 | 0.01# |
Description: #P < 0.05 meant statistically significant
Comparison in PCOS patients with pregnancy and without pregnancy
Analyses of the patient demographics and clinical characteristics were pre-specified. There were no significant differences in age, body mass index (BMI, kg/m2), the duration of infertility and PCOS, menstruation length, or gravidity or parity history between the two groups (Table 2). Of the 80 cases, 16 (20.0%) women got pregnant after the first ovulation treatment and 8 (10.0%) women got pregnant after the second ovulation treatment while 56 (70.0%) women received three treatments, with 2 women becoming pregnant successfully while the other 54 eventually failing. The average cycles of the all participants were 2.5, and 26 participants became pregnant, with a cumulative pregnancy rate reaching 32.5% (26/80), although 4 participants had spontaneous abortions and 4 received curettages due to the missed abortions. The rate of early pregnancy loss was 30.77% (8/26).
Table 2.
Characteristics of the participants at baseline
| Project | Pregnant group (n = 26) | Non-pregnant group (n = 54) | P |
|---|---|---|---|
| Maternal agea | 26 (25, 28) | 27.5 (25.8, 30) | 0.23 |
| BMI (kg/m2)b | 23.65 (21.23, 25.15) | 22.37 (21.59, 24.87) | 0.54 |
| Days for menstruationb | 60.0 (37.5, 77.5) | 44.0 (36.9, 63.8) | 0.47 |
| Months for infertilityb | 12.5 (8.5, 15.0) | 13 (4.8, 21.0) | 0.80 |
| Years for PCOSb | 1 (0, 3) | 1.5 (0.5, 2.6) | 0.55 |
| Previous pregnancy timeb | 0 (0, 1) | 0 (0, 0.25) | 0.98 |
| Parityb | 0 (0, 0) | 0 (0, 0.25) | 0.006 |
Description: Discrete variables above were all indicated as medians (quartiles)
aReferred to the t test
bReferred to the Wilcoxon rank-sum test
When the kisspeptin concentrations in the three phases in two groups were compared, there was a significant difference in the basal phase (P = 0.006) with 2293.0 ± 398.7 pg/ml in pregnancy and 1633.1 ± 203.8 pg/ml in non-pregnancy group. However, there was no significant difference in the other phases, nor the concentrations between the phases (Table 3). Moreover, the findings demonstrated a 95% confidence interval of 1511.5 to 3074.5 pg/ml for kisspeptin levels during the basal phase in pregnant women with PCOS. This result aligned with the hypothesis test for linearity based on the available samples. Further analysis of the basal LH and E2 levels in both groups revealed no statistical significance.
Table 3.
Comparison of Kisspeptin levels between the non-pregnant and pregnant group
| Period | Pregnant group | Non-pregnant group | P |
|---|---|---|---|
| (n=26, pg/ml) | (n=54, pg/ml) | ||
| Stage1a | 2293.0 ± 398.7 | 1633.1 ± 203.8 | 0.006# |
| Stage2b | 2506.8 ± 695.7 | 2107.6 ± 343.8 | 0.38 |
| Stage3a | 2392.4 ± 554.7 | 1952.0 ± 599.4 | 0.19 |
| Stage2-Stage1b | 213.7 ± 588.3 | 474.5 ± 537.1 | 0.62 |
| Stage3-Stage1a | 85.6 ± 486.0 | 319.0 ± 530.2 | 0.47 |
| Stage2-Stage3a | 114.4 ± 581.9 | 155.5 ± 757.3 | 0.93 |
aReferred to the t-test
bReferred to the Wilcoxon rank sum test
#P < 0.05 meant statistically significant
Discussion
Muir detected the mRNA expression of KISS-1R in the human hypothalamus for the first time in 2001 [9]. Researchers discovered that it could bind to the receptor on the neuron of gonadotropin-releasing hormone (GnRH), leading to the release of GnRH, the effects of which were time-and dose-dependent [10]. Apart from that, the kisspeptin/KISS-1R system expressed in the uterus and ovary plays a crucial role in the processes of ovulation and pregnancy [11].
The incidence of PCOS in women during the childbearing period ranges from 6.8 to 18.0%, with infertility accounting for 30–60% of the total [12, 13]. Ozlen [14] discovered that the levels of kisspeptin in women with PCOS were higher than in the normal group. In 2016, research was conducted in the First Hospital of Zhengzhou University [15], which indicated that the control group had a lower kisspeptin level in their follicular fluid than the PCOS group, whose KISS-1 gene was highly expressed in the granulosa cells. Excessive expression of kisspeptin promotes additional activation of the HPO axis, increasing the LH and follicle-stimulating hormone (FSH) ratios.
LE has been frequently utilized in the treatment of PCOS-based infertility since it was initially found to affect ovulation induction in 2000. As the third aromatase inhibitor, LE can release the synthesis of estrogen and restrain the negative feedback of the HPO axis. Therefore, gonadotropin secretion from the anterior pituitary is stimulated, which is helpful to follicle growth and development [16].
Meanwhile, increasing testosterone can either directly or indirectly increase the expression of the FSH receptor. Furthermore, as it does not influence the FSH receptor in the endometrium, LE enhances follicular sensitivity towards FSH [17].
Variation of kisspeptin during the menstrual cycle
Various hormones change regularly due to the precise regulation of the HPO axis during the menstrual cycle. Normally, the E2 level falls to the lowest at the basal level and has minimal negative feedback on the hypothalamus, promoting the release of GnRH. When it comes to the proliferative phase, the increasing level of E2 enhances the negative feedback and temporarily inhibits the release of GnRH. However, with the growth of the follicles, the E2 level increases up to 200 pg/ml or even higher, and the feedback becomes positive, inducing the LH and FSH peak, which is the signal before ovulation. In previous studies, kisspeptin has been identified as a potent stimulator of GnRH-dependent LH release [7], playing a dual role in both ovulation induction and mediating the feedback regulation E2 and GnRH/LH [18]. The results of our study revealed that kisspeptin was regularly expressed during the menstrual cycle of women with PCOS, which is lower during the basal period, peaks before ovulation, and then begins to fall in the luteal phase, showing a similar trend to the women having regular menstrual cycles, as documented by Zai [7]. In healthy women, the HPO axis acts positively during preovulation due to the positive feedback of estrogen, and the up-regulated KISS-1 genes induce a higher kisspeptin level. Instead, since the initial rise in serum progesterone level occurs between 48 h preovulation and 24 h post-ovulation, the hypothalamus suffers negative feedback. Therefore, the expression of the KISS-1 gene is reduced. However, unlike healthy women, there appeared to be no substantial difference in kisspeptin expression between phases in patients with PCOS, which could be due to one of two reasons. Firstly, PCOS has numerous subtypes [19, 20]. Secondly, the women with PCOS in the study may have other endocrine disorders, such as glucose intolerance, insulin resistance, and even abnormalities in the kisspeptin-neurokinin B (NKB) pathway, which has been extensively studied in recent years [21], which could result in reproductive abnormalities, introducing confounding factors.
In past research, there has been the same controversy over the relationship between kisspeptin and LH during the same period. Katulski mentioned that there was a correlation between the two hormones in both concentrations and secretion frequency in healthy women (cycle < 45 days), while there was no correlation in women with PCOS having irregular menstruation (cycle > 45 days) [19]. Katulski observed that excessive concentration and pulsatile secretion of kisspeptin were caused by impairment of the neuroendocrine hypothalamus system, and they appeared to worsen with disease progression. Furthermore, compared with the higher pulsatile secretion of kisspeptin, the pulsatile frequency of LH stimulated by GnRH did not change. It was proposed that neuroendocrine dysfunction could arise at the level of the kisspeptin receptor or during the signaling transduction of GnRH neurons.
Influence of LE on kisspeptin in women with PCOS
Based on previous researches, LE may change the gonadal hormone concentration in PCOS and decrease basal levels of LH, FSH, E2, and prolactin [17]. In this study, the basal level of kisspeptin also exhibited a lower level after the treatment of LE, without reaching a statistical significance. However, it is important to acknowledge potential limitations, as the study did not differentiate the single use of LE or the combination of LE and HMG which may have been underpowered, and the absence of classification into subtypes of PCOS might also have influenced the outcomes. Additionally, it is noteworthy that kisspeptin plays a significant role in central regulation, with its synthesis and secretion being notably more stable, providing a potentially more accurate reflection of the endocrine status in women with PCOS.
Balasch et al. coined the term “optimal LH dose” in 2001 [22], indicating that excessively high or low levels negatively impact follicular development. Previous immunohistochemical studies [23, 24] have confirmed that the LH receptor is initially expressed in cumulus cells, suggesting LH may exert an influence throughout the growth phase of oocytes. The marginal elevation observed in kisspeptin and LH levels following ovulation induction in this study could potentially enhance clinical symptoms and improve pregnancy rates among women with PCOS. This effect may be attributed to the altered hypothalamic-pituitary-gonadal axis and the subsequently heightened sensitivity of oocytes.
Predictive power of kisspeptin in early pregnancy
A successful pregnancy is dependent on the effective invasion of trophoblast cells. The KISS-1 gene and its receptor are expressed at the highest level in human peripheral tissues on the placental syncytiotrophoblast. Kisspeptin concentration may be a new and powerful biomarker for early pregnancy verification. In this study, the basal kisspeptin concentration in pregnant women diagnosed with PCOS exceeded that of the non-pregnant group. However, it is noteworthy that these results did not attain statistical significance, a circumstance that could be attributed to the limited sample size or the homogeneity in insulin resistance among the participants. Based on the results, 64% of pregnant women conceived during their first cycle. It appears that follicle development was delayed, while kisspeptin concentration decreased in the subsequent cycles, resulting in a lower pregnancy rate. We also analyzed the 95% confidence intervals of pregnant women diagnosed with PCOS in the hope of providing periodic data for the later reference range of kisspeptin in early pregnancy prediction, which requires a larger data set to corroborate the results.
As mentioned, previously, kisspeptin may stimulate the release of gonadotropin, making it much easier to reach the hormone thresholds and for ovulation to occur. This also serves as a reminder that women diagnosed with PCOS do not need to postpone fertility counseling until their endocrine abnormalities are resolved.
Conclusion
Kisspeptin plays a crucial role in regulating women’s reproductive endocrinology. Even in PCOS women, it also exhibited a regular occurrence throughout the menstrual cycle just like healthy women with a lower level during the menstrual period, peaks before ovulation, and then begins to fall in the luteal phase, although there was no significant difference which might be due to the insufficient sample size. The basal level of kisspeptin in PCOS decreases after LE treatment, which is probably beneficial for improving the endocrine disorder of PCOS patients. However, a higher rate of early pregnancy loss with PCOS remains an inevitable problem. Besides, the baseline kisspeptin level seems to hold potential as a predictor for sensitivity to ovulation treatment and the probability of early pregnancy. This may serve as a valuable tool for offering prognostic insights to guide clinical administration, promoting greater compliance among infertile women. However, further research is imperative to ascertain the connection between kisspeptin and early pregnancy, and the underlying mechanisms necessitate exploration in the future.
Acknowledgements
We would like to thank The First Affiliated Hospital of Chongqing Medical University for providing the scientific research support for this manuscript.
Abbreviations
- PCOS
Polycystic ovary syndrome
- HCG
Human chorionic gonadotropin
Author contribution
Wenwu Gui conceived the idea, performed the data analysis, and wrote the original draft. Qiao Peng conceived the idea, performed the data collection and wrote the main manuscript text and prepared all figures. Siting Lv, Yidi Wen, and Lianlian Wang performed the data collection and analysis and investigation. All authors read and approved the final manuscript.
Funding
This study was funded by the Science and Technology Planning Project of Yuzhong District of Chongqing City, China (No: 20190124).
Data availability
The datasets used and/or analyzed during the current study available from the corresponding author on reasonable request.
Declarations
Ethics approval and consent to participate
This study was conducted with approval from the Ethics Committee of The First Affiliated Hospital of Chongqing Medical University (Approval Number: 242/2019), and registered in the Chinese Clinical Trial Register website (www.chictr.org.cn, ChiCTR2300071389) on May 14, 2023. This study was conducted in accordance with the declaration of Helsinki. Written informed consent was obtained from all participants.
Consent for publication
Not applicable.
Competing interests
The authors declare no competing interests.
Disclaimer
The funding body had no role in the design of the study and collection, analysis, and interpretation of data and in writing the manuscript.
Footnotes
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
References
- 1.Hu KL, Chang HM, Zhao HC, Yu Y, Li R, Qiao J. Potential roles for the kisspeptin/kisspeptin receptor system in implantation and placentation. Hum Reprod Update. 2019;25(3):326–43. 10.1093/humupd/dmy046. 10.1093/humupd/dmy046 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Xu L, Xue H, Li S, Xu J, Chen L. Seasonal differential expression of KiSS-1/GPR54 in the striped hamsters (Cricetulus barabensis) among different tissues. Integr Zool. 2017;12(3):260–8. 10.1111/1749-4877.12223. 10.1111/1749-4877.12223 [DOI] [PubMed] [Google Scholar]
- 3.Xu R, Yan Y, Xie MH. The feedback mechanism of sex steroid regulating ARC and AVPV nuclei in the hypothalamic by the kisspeptin-GPR54 signaling pathway. Chin J Biochem Mol Biol. 2018;34(8):810–7. 10.13865/j.cnki.cjbmb.2018.08.02. Accessed 24 Aug 2018.
- 4.Li M, Jiang F, Wei X. Study on the effect and mechanism of kisspeptin on apoptosis of islet β cells. Fujian Med J. 2020;42(1):125–7. [Google Scholar]
- 5.Expert Group of Consensus on In fertility Management & Fertility Preservation Related to Polycystic Ovary Syndrome;Reproductive Endocrinology & Fertility Preservation Section of Chinese Society on Fertility Preservation under Chinese Preventive Medicine Association. Consensus on infertility management and fertility preservation related to polycystic ovary syndrome. Reproductive Med. 2020;29(7):843–51. [Google Scholar]
- 6.Liao X, Yang YJ. Clinical trial of letrozole combined with metfbrmin on obese polycystic ovary syndrome with infertility. Chin J Clin PharmacoI. 2023;39(21):3058–62. [Google Scholar]
- 7.Zhai J, Ding L, Zhao S, Li W, Sun Y, Su S, Zhang J, Zhao H, Chen ZJ. Kisspeptin: a new marker for human pre-ovulation. Gynecol Endocrinol. 2017;33(7):560–3. 10.1080/09513590.2017.1296129. 10.1080/09513590.2017.1296129 [DOI] [PubMed] [Google Scholar]
- 8.Rotterdam ESHRE/ASRM-Sponsored PCOS Consensus Workshop Group. Revised 2003 consensus on diagnostic criteria and long-term health risks related to polycystic ovary syndrome. Fertil Steril. 2004;81(1):19–25. 10.1016/j.fertnstert.2003.10.004. 10.1016/j.fertnstert.2003.10.004 [DOI] [PubMed] [Google Scholar]
- 9.Muir AI, Chamberlain L, Elshourbagy NA, Michalovich D, Moore DJ, Calamari A, Szekeres PG, Sarau HM, Chambers JK, Murdock P, Steplewski K, Shabon U, Miller JE, Middleton SE, Darker JG, Larminie CG, Wilson S, Bergsma DJ, Emson P, Faull R, Philpott KL, Harrison DC. AXOR12, a novel human G protein-coupled receptor, activated by the peptide KiSS-1. J Biol Chem. 2001;276(31):28969–75. 10.1074/jbc.M102743200. 10.1074/jbc.M102743200 [DOI] [PubMed] [Google Scholar]
- 10.Feng T, Wei SL, Xu XL. Effects of kisspeptin and N-carbamylgulamate on GnRH secretion in GT1-7 cells. Chin J Biol. 2019;36(6):47–5058. [Google Scholar]
- 11.Kou LC, Luo QQ, Shi Y. The function of kisspeptin/kiss1 r system expressed in the corpus luteum during the pathogenesis of spontaneous abortion rats. BMU J. 2016;39(6):401–403452. [Google Scholar]
- 12.Liu BW, Bao ST, Yang YQ. Comparison of pregnancy outcomes of three controlled ovarian stimulation protocols for patients with polycystic ovary syndrome. J Reprod Med. 2019;28(12):1396–401. [Google Scholar]
- 13.Ni JL, Peng X. Clinical effects of different ovulation induction schemes in infertile women with polycystic ovary syndrome. Chin Matern Child Hlth Care. 2019;34(22):5252–4. [Google Scholar]
- 14.Emekci Ozay O, Ozay AC, Acar B, Cagliyan E, Seçil M, Küme T. Role of kisspeptin in polycystic ovary syndrome (PCOS). Gynecol Endocrinol. 2016;32(9):718–22. 10.3109/09513590.2016.1161019. 10.3109/09513590.2016.1161019 [DOI] [PubMed] [Google Scholar]
- 15.Guo W, Yao GD, Xing ZM. Kisspeptin participates in the regulation of estrogen and progesterone secretion in granu-losa cells derived from polycystic ovarian syndrome. Prog Obstet Gynecol. 2019;28(3):190–3. [Google Scholar]
- 16.Qi Y, Ma W, Liu YY. Research progress of letrozole in the treatment of polycystic ovary syndrome. J Shenyang Med Coll. 2020;22(5):472–5. [Google Scholar]
- 17.Wang D, Sun L, Yang GY, et al. Effect of modified Cangfu Daotan decoction combined with letrozole on ovulation induction and reproductive hormone in patients with polycystic ovary syndrome. Chin Arch Tradit Chin Med. 2019;37(3):717–20. [Google Scholar]
- 18.D’Occhio MJ, Campanile G, Baruselli PS. Peripheral action of kisspeptin at reproductive tissues-role in ovarian function and embryo implantation and relevance to assisted reproductive technology in livestock: a review. Biol Reprod. 2020;103(6):1157–70. 10.1093/biolre/ioaa135. 10.1093/biolre/ioaa135 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Katulski K, Podfigurna A, Czyzyk A, Meczekalski B, Genazzani AD. Kisspeptin and LH pulsatile temporal coupling in PCOS patients. Endocrine. 2018;61(1):149–57. 10.1007/s12020-018-1609-1. 10.1007/s12020-018-1609-1 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20.Tang R, Ding X, Zhu J. Kisspeptin and polycystic ovary syndrome. Front Endocrinol (Lausanne). 2019;10:298. 10.3389/fendo.2019.00298. 10.3389/fendo.2019.00298 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21.Zhang X, Zheng Y, Guo Y, Lai Z. The effect of low carbohydrate diet on polycystic ovary syndrome: a meta-analysis of randomized controlled trials. Int J Endocrinol. 2019;2019:4386401. 10.1155/2019/4386401. 10.1155/2019/4386401 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 22.Balasch J, Creus M, Fábregues F, Civico S, Carmona F, Puerto B, Casamitjana R, Vanrell JA. The effect of exogenous luteinizing hormone (LH) on oocyte viability: evidence from a comparative study using recombinant human follicle-stimulating hormone (FSH) alone or in combination with recombinant LH for ovarian stimulation in pituitary-suppressed women undergoing assisted reproduction. J Assist Reprod Genet. 2001;18(5):250–6. 10.1023/a:1016662100572. 10.1023/a:1016662100572 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 23.Baena V, Owen CM, Uliasz TF, Lowther KM, Yee SP, Terasaki M, Egbert JR, Jaffe LA. Cellular heterogeneity of the luteinizing hormone receptor and its significance for cyclic GMP signaling in mouse preovulatory follicles. Endocrinology. 2020;161(7):bqaa074. 10.1210/endocr/bqaa074. 10.1210/endocr/bqaa074 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 24.von Wolff M, Eisenhut M, Stute P, Bersinger NA. Gonadotrophin stimulation reduces follicular fluid hormone concentrations and disrupts their quantitative association with cumulus cell mRNA. Reprod Biomed Online. 2022;44(1):193–9. 10.1016/j.rbmo.2021.08.018. 10.1016/j.rbmo.2021.08.018 [DOI] [PubMed] [Google Scholar]
Associated Data
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Data Availability Statement
The datasets used and/or analyzed during the current study available from the corresponding author on reasonable request.