A Comprehensive Review of Infertility Outcomes Associated with Obesity and Polycystic Ovary Syndrome (PCOS)

Abstract

Polycystic ovarian syndrome (PCOS) is one of the most prevalent endocrine conditions affecting women of reproductive age, and it is among the main causes of anovulatory infertility. The prevalence of PCOS is approximated to be between 6 and 15% worldwide based on the diagnostic criteria. The distinguishing characteristics of PCOS include polycystic ovarian morphology, chronic anovulation, and hyperandrogenism, characteristically linked with metabolic dysfunction and insulin resistance. Studies have shown that up to 80% of women with PCOS are overweight or obese, pointing to the greater prevalence of obesity, notably visceral fat accumulation. In cases where obesity and PCOS coexist, they considerably exacerbate both metabolic and reproductive phenotypes. Obesity negatively impacts infertility due to its interference in folliculogenesis, endometrial receptivity, and the hypothalamic-pituitary-ovarian (HPO) axis. When PCOS and obesity coexist, they aggravate hyperinsulinemia, insulin resistance, and hyperandrogenism, resulting in severe anovulatory cycles, reduced oocyte quality and implantation rates, along with greater susceptibility to miscarriage. Moreover, reduced pregnancy rates, increased demand for ART, and adverse pregnancy outcomes, such as gestational diabetes and pre-eclampsia, are correlated with obese women with PCOS. Current understanding of the relationship between obesity, PCOS, and infertility is summarized in this review. This review article evaluates the pathophysiological processes connecting these conditions, examines the clinical data supporting their association, and analyzes medical interventions. To conclude, it analyzes the adoption of precision medicine, newer biomarkers, and metabolic therapies as a future approach to facilitate fertility outcomes in obese women with PCOS.

Keywords

Introduction

About 8–12% of couples worldwide experience infertility, with female factors accounting for nearly half of all cases (1). Infertility is a growing global health concern. Up to 70–80% of anovulatory infertility is caused by polycystic ovarian syndrome (PCOS), one of the most common causes of female infertility among the different etiologies (2). PCOS is a complex endocrine condition with symptoms related to metabolism, reproduction, and psychology. Since PCOS affects fertility as well as long-term health, raising the risk of type 2 diabetes mellitus (T2DM), cardiovascular disease, and endometrial cancer, its clinical heterogeneity makes it an especially difficult condition to manage (3). Obesity is one of the key variables affecting the severity and clinical manifestation of PCOS. Although lean women may develop PCOS, 40–80% of cases—depending on the population under study—involve obesity (4). Obesity and PCOS have a complex and reciprocal relationship: PCOS itself predisposes women to weight gain and difficulty maintaining weight loss due to intrinsic metabolic and hormonal disturbances, while obesity exacerbates the clinical and metabolic features of PCOS (5). One known risk factor for subfertility and unfavorable reproductive outcomes is obesity alone. Obesity is linked to anovulation, irregular menstruation, decreased rates of conception, and increased pregnancy loss in women without PCOS (6). Insulin resistance, changes in gonadotropin secretion, oocyte quality, and impaired endometrial receptivity are some of the mechanisms through which this happens (7). These processes are exacerbated when obesity and PCOS coexist, which has a detrimental synergistic effect on fertility potential.

According to epidemiology, the prevalence of PCOS and obesity is rising globally, which poses serious issues for reproductive health. The clinical burden of infertility associated with PCOS is rising in tandem with the global increase in obesity rates (8). Furthermore, obesity decreases the effectiveness of assisted reproductive technologies (ART) in addition to impairing natural fertility outcomes. In comparison to their leaner counterparts, obese and PCOS-afflicted women frequently need higher gonadotropin dosages, have lower oocyte yields, and have worse implantation and live birth rates (9). It is impossible to overestimate the significance of treating obesity in relation to infertility caused by PCOS. It has been demonstrated that even a small weight loss of 5–10% can improve menstrual regularity, restore ovulation, and raise the likelihood of a spontaneous pregnancy (10). For obese women with PCOS who want to become pregnant, lifestyle changes are therefore regarded as first-line treatment. Fertility outcomes are further improved by pharmacological interventions, such as anti-androgens, ovulation induction agents, and insulin sensitizers like metformin (11).

Although ART's success rates are greatly increased when weight loss is achieved before treatment, it is still a viable option in situations where conservative management is ineffective (12). Since obesity has a significant effect on the metabolic and reproductive outcomes of women with PCOS, it is crucial to comprehend how these conditions interact to optimize management techniques. The detrimental reproductive effects of obesity in PCOS have been mediated by insulin resistance, hyperinsulinemia, adipokine dysregulation, and chronic low-grade inflammation, according to research conducted over the past 20 years (13,14). There are still a lot of unanswered questions regarding the molecular foundations and the most effective approaches to customized care, though.

The relationship between obesity, PCOS, and infertility will be thoroughly summarized in this review. The pathophysiological mechanisms by which obesity aggravates PCOS will be examined first, with particular attention paid to insulin resistance, inflammation, adipokines, endometrial receptivity, and dysfunction of the HPO axis. The clinical data relating obesity and PCOS to infertility outcomes in both natural conception and assisted reproductive technology settings will then be compiled. Lastly, it will go over management strategies, from changing one's lifestyle to using cutting-edge fertility treatments, and it will point out future research avenues that hope to improve fertility outcomes in this high-risk group.

PATHOPHYSIOLOGICAL MECHANISMS LINKING OBESITY AND PCOS

The bidirectional relationship between obesity and PCOS is triggered by a complex network of endocrine, metabolic, and inflammatory disturbances. Obesity exacerbates PCOS's clinical severity and impairs fertility outcomes, even though the condition is essentially an ovarian dysfunction disorder marked by hyperandrogenism and chronic anovulation. Obesity adds to the development of PCOS and infertility through several overlapping mechanisms, including insulin resistance, endometrial dysfunction and hyperinsulinemia, adipokine imbalance, chronic inflammation, and HPO axis dysfunction.

Regardless of body mass index, it is estimated that up to 70% of women with PCOS have insulin resistance (15). Obese women possess excess visceral fat, specifically those with central adiposity, which releases pro-inflammatory cytokines and free fatty acids that disrupt insulin signaling in the liver, skeletal muscle, and adipose tissue, which in turn encourages hyperinsulinemia, resulting in worsening of metabolic and reproductive dysfunction. At the ovarian level, insulin and luteinizing hormone (LH) work together to stimulate production of androgen by theca cells (16). Elevated insulin levels suppress the hepatic synthesis of sex hormone-binding globulin (SHBG), raising free circulating testosterone. This results in hyperandrogenism, which impairs follicular development, leading to chronic anovulation. Clinical manifestations include acne, hirsutism, and menstrual irregularities, each of which is severe in obese women with PCOS(17). Granulosa cell function is altered by hyperinsulinemia, hindering the production of estradiol and interfering with oocyte maturation. This gives rise to reduced oocyte quality and disrupted embryo development in both natural and assisted conception cycles (18). Therefore, insulin resistance is a major mechanistic link between infertility and obesity in PCOS.

The normal female reproduction depends on the cyclic secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamus, which regulates LH and follicle-stimulating hormone (FSH) secretion. GnRH pulsatility is accelerated in PCOS, which favors LH secretion over FSH (19). Moreover, obesity worsens this delicate balance.

Hyperinsulinemia and hyperleptinemia, commonly associated with obesity, alter hypothalamic sensitivity to negative feedback by estradiol and progesterone. This leads to persistently elevated LH, while FSH fails to adequately support normal follicular maturation. This environment induces the development of multiple small antral follicles without aggravating to a dominant follicle, leading to follicular arrest and chronic anovulation (20). The synergistic effects of PCOS and obesity on the HPO axis result in a greater occurrence of menstrual irregularities and infertility compared to that in lean PCOS women. Studies have shown that obese women with PCOS exhibit more worsened ovulatory dysfunction and profound disturbances in gonadotropin secretion (21).

Adipose tissue is not solely an energy storage depot but also an active endocrine organ. It secretes adipokines a bioactive peptide that control insulin sensitivity, reproductive function, and metabolism. Adipokines include leptin, adiponectin, resistin, and visfatin. Leptin levels are associated with body fat mass. Hypothalamic leptin resistance is seen in the case of hyperleptinemia in obesity, disrupting appetite control and energy balance. In addition, the ovary and endometrium are directly affected by elevated levels of leptin, hindering steroidogenesis and implantation (22). Adiponectin levels are dropped in cases of obesity and PCOS. It enhances insulin sensitivity and contributes to metabolic dysfunction and insulin resistance (23). Resistin and visfatin being pro-inflammatory adipokines are implicated in PCOS pathophysiology, contributing to abnormal steroidogenesis and chronic inflammation, and disrupting fertility (24). Endocrine dysregulation of adipokines in obesity–PCOS interaction not only exacerbate metabolic derangements but also oocyte competence and uterine receptivity, diminishing the likelihood of successful conception (25).

Obesity and PCOS are often associated with chronic low-grade inflammation. In obese women, adipose tissue is infiltrated by macrophages and releases inflammatory cytokines such as interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and C-reactive protein, impairing insulin signaling, altering ovarian steroidogenesis, and also inducing oxidative stress (26). In individuals with PCOS, inflammation exacerbates ovarian dysfunction and hyperandrogenism. Anovulation, poor oocyte quality, and reduced implantation rates have been correlated with elevated levels of inflammatory markers (27). In addition, iinflammatory pathways augment the risk of miscarriage as they impair endometrial receptivity. Consequently, inflammation has a significant association with obesity, PCOS, and infertility. Successful conception relies not only on  quality of oocyte and ovulation but also on endometrial receptivity. Both PCOS and obesity tend to impair endometrial function, which in turn leads to  failure of implantation and early pregnancy loss. Hyperandrogenism and hyperinsulinemia are capable of modifying the expression of endometrial receptivity markers including glycodelin and integrins. Additionally, chronic inflammation interrupts the decidualization process that is vital for embryo implantation (28). Obese females diagnosed with PCOS undergoing assisted reproductive technology (ART)  manifest lower implantation and pregnancy rates despite of  possessing structurally normal embryos emphasizing the role of endometrial dysfunction (29).

Recent findings advocate that oxidative stress and  mitochondrial dysfunction may have a pivotal role in the infertility associated with PCOS and obesity. Excess adiposity elevates the level of reactive oxygen species (ROS) production. These elevated levels might damage oocytes and lowers their development potential. Mitochondrial abnormalities have been reportedly observed in the oocytes of women with PCOS and obesity , driving impaired  fertilization and embryo development (30).

CLINICAL EVIDENCE LINKING OBESITY, PCOS, AND INFERTILITY

Obese women with PCOS have notable clinical manifestations since it has a deleterious effect on reproductive function, ART and pregnancy outcomes. PCOS solely causes anovulatory infertility, and concurrence with obesity exacerbates the severity of subfertility. Numerous epidemiological studies have affirmed the association of obesity in suppression of fecundity and prolonged time to conception. It is found that obese women have  a two- to three-fold escalation in risk of infertility, even after adjusting for age and distorting variables (31). The vital mechanism is oligo- or anovulation, including altered luteal function and impaired endometrial receptivity contribution.  Obesity amplifies the risk of miscarriage, irrespective of age or underlying infertility diagnosis. Increased levels of pro-inflammatory cytokines and insulin damage embryo-endometrial dialogue, intensifying miscarriage rates (32). Obese women undergoing in vitro fertilization (IVF) demand higher gonadotropin doses, possess lower oocyte retrieval rates, lessened embryo quality, and lowered pregnancy and live birth rates compared with normal-weight women (33). Thus, obesity solely leads to substantial burden on fertility, and when concomitant with PCOS, its consequences become even more pronounced.

Approximately 70-80% of cases of anovulatory infertility is contributed by PCOS,  resulting in clinical manifestations such as poor oocyte quality, endometrial dysfunction and oligo-/anovulation (34). Even though lean women with PCOS also face difficulties with conceiving but obesity worsens this occurrence. In women with PCOS, chronic anovulation is resulted from hyperandrogenism and HPO axis dysfunction.  Obese women with PCOS suffer from frequent anovulatory cycles in compared with lean women (35). Amenorrhea and  oligomenorrhea are more prevalent resulting from greater insulin resistance and excess androgen in obese women with PCOS. Gestational diabetes, preterm delivery, hypertensive disorder risks increase with obese women with PCOS (36).The combination of obesity with PCOS leads to more critical  infertility than either condition alone. In contrast to that seen in lean PCOS women , obese women with PCOS take remarkably longer time for conception (37). Clinical findings have shown that oocytes collected during retrieval from obese women with PCOS reflect diminished increased oxidative stress, meiotic competence, and abnormal mitochondrial function. This results in lowered fertilization and embryo developmental potential (38).  Recent studies regarding ART revealed that obese women with PCOS have lower rates of implantation even when high- quality embryo is implanted, indicating intrinsic endometrial dysfunction (39). Obese women with PCOS  have a marked risk of miscarriage, in contrast to lean women with PCOS. Furthermore, complications associated with pregnancy, such as pre-eclampsia and gestational diabetes, are likely to occur more in this population (40). Thus, weight management plays a vital role in optimizing fertility outcomes in women with PCOS.

CLINICAL INTERVENTIONS

Clinical interventions in the management of women with PCOS and obesity is a multidimensional sequential approach. These interventions span from lifestyle modification to pharmacological therapies to assisted reproductive technologies. Lifestyle modification is one of the first-choice therapies for obese women with PCOS attempting to achieve successful conception. Research outcomes have demonstrated that minimal weight loss up to 5-10% can boost menstrual regularity,  revive ovulation, and optimize successful conception rates strikingly  (41). A low postprandial glucose-inducing diet is recommended to enhance insulin sensitivity and considerably lower the levels of androgen. Usually, a diet rich in vegetables, particularly leafy greens and non-starchy vegetables, fruits like fresh berries, apples, guava, oranges, high-fiber grains such as oats, brown rice, quinoa and rye and unsaturated fats tends to enhance reproductive and metabolic effects (42). Exercises such as aerobic and muscle-strengthening training collectively boost insulin sensitivity and also facilitate weight loss. In obese women with PCOS, supervised exercise regimens have reportedly augmented ovulation and successful conception frequency (43). Evidence also suggests that cognitive-behavioral interventions aid in sustaining long-term lifestyle modification and also focus on the psycho-social impact of PCOS, featuring anxiety and depression. These modifications in lifestyle assist not only in improving fertility but also in boosting cardio-metabolic health and reducing the risk of long-term diseases.

Pharmacological interventions have far-reaching implications in the management of PCOS in association with obesity and employ pharmacological therapies such as insulin sensitizers, such as metformin, thiazolidinediones, and inositols, ovulation inducers-clomiphene citrate, letrozole, gonadotropins, and androgen antagonists. Metformin is the most preferred type of insulin sensitizer in the treatment of PCOS. It is capable of enhancing insulin sensitivity, lowering androgen levels, attenuating hyperinsulinemia and restoring menstrual cyclicity. Metformin showed enhanced effects on ovulation and pregnancy rate during randomized trials when paired with ovulation inducers (44). Novel agents namely thiazolidinediones and inositols have shown a promising effect in optimizing metabolic and reproductive outcomes, although evidence for their use is not well established (45). Ovulation inducers are usually indicated when insulin sensitizers and lifestyle modification fail to produce desirable outcomes. The first- line therapy includes Clomiphene citrate; however higher doses are required since obese women with PCOS often express clomiphene resistance. Letrozole is an aromatase inhibitor, capable of stimulating ovulation and securing live births, notably in obese women diagnosed with PCOS. Moreover, it has been proven to be superior to that of clomiphene citrate. The available clinical data support its safety and efficacy (46). Women unresponsive to oral agents can be administered with gonadotropins, yet they impose a risk of ovarian hyperstimulation syndrome (OHSS) and multiple pregnancy. Nevertheless, careful vigilant monitoring is crucial.  Spironolactone and cyproterone acetate are the anti- androgenic agents that manage acne and hirsutism, but they are not typical fertility-boosting drugs. But they should be ceased before trying to conceive due to teratogenic risk.

ART is endorsed if initial clinical management interventions prove ineffective. Conversely, the success rates of ART in obese women are reduced through various mechanisms, specifically impairing oocyte quality, dysregulated hormonal milieu and compromised endometrial receptivity. Compared to that of women of normal- weight, obese women with PCOS demand greater doses of gonadotropin, experience lower number of pregnancies and possess reduced oocyte retrieval per cycle during in vitro fertilization (IVF) (47). The beneficial outcomes of Intracytoplasmic sperm injection (ICSI) are hampered in obese women with PCOS including diminished implantation rates and embryo quality. Most vital factor to be considered prior to ART is marked weight reduction. Studies have demonstrated that this will impose a positive impact, also emphasizing the necessity of pre-treatment counseling (48). In women with higher BMI (BMI ≥ 35–40 kg/m²), classified as obese women refractory towards lifestyle modifications, bariatric surgery serves as a valuable intervention. Post-bariatric surgery obese women demonstrate a revival in ovulation, menstrual regularity, lowered androgen levels, further favoring fertility (49). Post-bariatric conception has shown positive outcomes than conception in women without undergoing surgical procedures. Post-surgery, conception should be postponed for at least 12-18 months to facilitate nutritional status and achieve a stable weight (50). Obesity and PCOS cause psychological distress, which should not be overlooked. Major concerns include body image concerns, depression and anxiety. Obesity and PCOS have a detrimental effect on quality of life and therapy adherence. It is essential to integrate counselling and mental health support within fertility care to achieve better results and patient well-being (51).

Emerging Trends and Future Research Directions

Despite considerable advancements in determining the association between PCOS, obesity, and infertility, there remains a research gap in accordance with both clinical and pathophysiological insights. Tackling these research gaps is vital in enhancing fertility outcomes in this population with heightened risk factors.  A “one-size-fits-all” strategy is employed currently for the treatment of PCOS in obese women. Even so, recent studies stress pronounced heterogeneity in reproductive, metabolic, and hormonal presentations. For further development of personalized therapies, precision medicine approaches integrating genetic, epigenetic, and metabolic profiling can be utilized. For instance, women with marked insulin resistance can benefit from insulin sensitizers, whereas those with hyperandrogenic phenotypes are more likely to respond to ovulation stimulation and anti-androgenic therapies (52). The existing criteria for the diagnosis of PCOS include the Rotterdam criteria, which fail to cover the entire range of phenotypes. The identification of new biomarkers, such as inflammatory markers, adipokines, and anti-Mullerian hormone (AMH) may aid in early diagnosis and risk profiling of the condition (53). To enhance ART success rates and customize fertility treatment in obese women with PCOS, biomarkers of endometrial receptivity are beneficial.

Novel research emphasizes that the gut microbiome may act as a potential mediator between PCOS, infertility, and obesity. In obese individuals with PCOS, dysbiosis has been linked with systemic inflammation, insulin resistance, and altered steroid metabolism (54). Gut microbiome modulation through probiotics, prebiotics or transplantation of fecal microbiota is a promising focus for future exploration with significant outcomes in restoring fertility. The newer drug inositol, including its isomers myo-inositol and D-chiro-inositol, has demonstrated promising improvement in insulin sensitivity and in the restoration of ovulatory function. GLP-1 receptor agonists, previously used in the treatment of obesity and type 2 diabetes, may lower body weight and enhance fertility outcomes in obese women with PCOS (55). Omega-3 fatty acids and vitamin D supplements may modulate chronic inflammation and facilitate fertility outcomes (56). These newer therapies, alongside standard therapy, could add to the available range of therapies for this condition. Apart from clinical interventions, addressing obesity on a public health scale is pivotal. With an increase in obesity rates globally, the impact of PCOS-related infertility is predicted to expand. The rate and intensity of PCOS and its reproductive consequences can be reduced using early intervention, lifestyle education, and tackling obesity in children through targeted public health strategies (57).

CONCLUSION

PCOS and obesity are two associated conditions that strongly influence fertility in females. The coexistence of obesity along with PCOS exacerbates metabolic, hormonal, and fertility impairment, while PCOS alone can be a major cause for infertility due to anovulation.

The processes underlying this association involve multiple contributing factors, such as elevated androgen levels, reduced insulin responsiveness, hypothalamic–pituitary–ovarian axis disruption, chronic inflammation, decreased uterine receptivity, and adipokine imbalance. Obese women with PCOS face clinical complications, including longer time to conception, reduced embryo quality, higher miscarriage risk, lower oocyte quality, and lower implantation rates.

Management of obesity in PCOS is an integrated approach initiated with lifestyle modification, which remains the cornerstone of therapy. Insulin sensitizers and ovulation induction drugs possess favorable outcomes. Assisted reproductive technologies (ART) are utilized when frontline therapies fail to achieve the desired outcomes. In cases of severe obesity, bariatric surgery confers benefits in selected cases.  Nevertheless, psychological support is critical in managing the emotional burden of infertility. Prospectively, progress in novel biomarkers, precision medicine, and emerging pharmacotherapies holds potential to enhance effectiveness and provide personalized treatment strategies. Concurrently, community level interventions are necessary to combat the overall burden of infertility associated with PCOS.In the long run, confronting obesity as a modifiable risk factor exemplifies the most impactful strategy to improve reproductive outcomes in women with PCOS. Clinical care, research and public health must therefore work hand in hand to address the overlapping challenges of PCOS, obesity, and infertility.

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