Association Between Body Mass Index and Female Infertility in the United States: Data from National Health and Nutrition Examination Survey 2013–2018

No evidence of genetic causation between iron and infertility: a Mendelian randomization study

Background

Observational studies have explored the impact of iron homeostasis on infertility; however, establishing definitive causal relationships remains challenging. This study utilized a two-sample Mendelian randomization approach to investigate the potential causal relationship between iron status and infertility.

Materials and methods

Four indicators of iron status-serum iron, ferritin, transferrin saturation, and total iron binding capacity, were considered as exposure factors. Infertility was the outcome variable for both men and women. Robust causality was assessed using the primary inverse-variance-weighted method, complemented by three supplementary Mendelian randomization approaches. Sensitivity analyses were performed to enhance the precision and reliability of the results.

Results

No statistically significant associations were identified between the four indicators of iron status and infertility. These results remained consistent across multiple Mendelian randomization methodologies.

Conclusion

In conclusion, there is no evidence of a genetic causal relationship between iron status and infertility. Nevertheless, this does not preclude the possibility of a connection between iron status and infertility at different mechanistic levels.

Association between frozen embryo transfer and childhood allergy: a retrospective cohort study

RESEARCH QUESTION

Does frozen embryo transfer (FET) increase the risk of allergic diseases in offspring?

DESIGN

This study followed up 653 singleton children: 166 born through FET and 487 born through natural conception. Demographic characteristics, perinatal information and allergic diseases of children and their parents were collected through clinical medical systems and questionnaires. Among these 653 children, allergen-specific immunoglobulin E (IgE) testing was performed using peripheral blood samples collected from 207 children: 145 in the FET group and 62 in the natural conception group. The prevalence of allergic diseases and positive rates of allergen-specific IgE testing were compared between the two groups with adjustments for confounding factors.

RESULTS

The prevalence of food allergy was significantly higher in children born through FET compared with children born through natural conception (adjusted OR = 3.154, 95% CI 1.895-5.250; P < 0.001). In addition, positive rates of food allergen sensitization were higher in children in the FET group compared with children in the natural conception group (adjusted OR = 5.769, 95% CI 2.859-11.751, P < 0.001). Children in the FET group had a higher positive sensitization rate to at least one allergen compared with children in the natural conception group (adjusted OR = 3.127, 95% CI 1.640-5.961, P < 0.001). No association was observed between FET and other allergic diseases, including asthma (P = 0.136), atopic dermatitis (P = 0.130) and allergic rhinitis (P = 0.922). Allergen sensitization IgE testing indicated no differences between the two groups in terms of positive sensitization rates of other common allergens, including animal and insect allergens (P = 0.627), inhaled outdoor allergens (P = 0.915) and inhaled outdoor allergens (P = 0.544).

CONCLUSION

This study suggests that children born through FET have increased risk of developing food allergy in early childhood.

Effects of Calorie Restriction on Preserving Male Fertility Particularly in a State of Obesity

PURPOSE OF REVIEW

Highlight the importance of exploring nutritional interventions that could be applied as alternative or supplementary therapeutic strategies to enhance men's fertility.

RECENT FINDINGS

Lifestyle choices have prompted extensive discussions regarding its implications and applications as a complementary therapy. The growing concern over the decline in sperm quality underscores the urgency of investigating these alternative interventions. Calorie restriction (CR) has emerged as a promising strategy to improve male fertility. The efficacy of CR depends on factors like age, ethnicity and genetics. Clinical studies, such as CALERIE, have shown an improvement in serum testosterone level and sexual drive in men with or without obesity. Additionally, CR has been shown to positively impact sperm count and motility; however, its effects on sperm morphology and DNA fragmentation remain less clear, and the literature has shown discrepancies, mainly due to the nature of technically dependent assessment tools. The review advocates a personalized approach to CR, considering individual health profiles to maximize its benefits. It underscores the need for routine, accessible diagnostic techniques in male reproductive health. It suggests that future research should focus on personalized dietary interventions to improve male fertility and overall well-being in individuals with or without obesity and unravel CR's immediate and lasting effects on semen parameters in men without obesity.

Predictors of success after in vitro fertilization

The last few decades have witnessed a rise in the global uptake of in vitro fertilization (IVF) treatment. To ensure optimal use of this technology, it is important for patients and clinicians to have access to tools that can provide accurate estimates of treatment success and understand the contribution of key clinical and laboratory parameters that influence the chance of conception after IVF treatment. The focus of this review was to identify key predictors of IVF treatment success and assess their impact in terms of live birth rates. We have identified 11 predictors that consistently feature in currently available prediction models, including age, duration of infertility, ethnicity, body mass index, antral follicle count, previous pregnancy history, cause of infertility, sperm parameters, number of oocytes collected, morphology of transferred embryos, and day of embryo transfer.

Food, nutrition, and fertility: from soil to fork

Food and nutrition-related factors, including foods and nutrients consumed, dietary patterns, use of dietary supplements, adiposity, and exposure to food-related environmental contaminants, have the potential to impact semen quality and male and female fertility; obstetric, fetal, and birth outcomes; and the health of future generations, but gaps in evidence remain. On 9 November 2022, Tufts University's Friedman School of Nutrition Science and Policy and the school's Food and Nutrition Innovation Institute hosted a 1-d meeting to explore the evidence and evidence gaps regarding the relationships between food, nutrition, and fertility. Topics addressed included male fertility, female fertility and gestation, and intergenerational effects. This meeting report summarizes the presentations and deliberations from the meeting. Regarding male fertility, a positive association exists with a healthy dietary pattern, with high-quality evidence for semen quality and lower quality evidence for clinical outcomes. Folic acid and zinc supplementation have been found to not impact male fertility. In females, body weight status and other nutrition-related factors are linked to nearly half of all ovulation disorders, a leading cause of female infertility. Females with obesity have worse fertility treatment, pregnancy-related, and birth outcomes. Environmental contaminants found in food, water, or its packaging, including lead, perfluorinated alkyl substances, phthalates, and phenols, adversely impact female reproductive outcomes. Epigenetic research has found that maternal and paternal dietary-related factors can impact outcomes for future generations. Priority evidence gaps identified by meeting participants relate to the effects of nutrition and dietary patterns on fertility, gaps in communication regarding fertility optimization through changes in nutritional and environmental exposures, and interventions impacting germ cell mechanisms through dietary effects. Participants developed research proposals to address the priority evidence gaps. The workshop findings serve as a foundation for future prioritization of scientific research to address evidence gaps related to food, nutrition, and fertility.

The association of Life's Simple 7 and infertility among U.S. women

Background

The Life's Simple 7 (LS7) metric is a comprehensive measure of cardiovascular health (CVH) that encompasses seven distinct risk factors and behaviors associated with cardiovascular disease (CVD). Some studies have shown an association between infertility and CVD. The present study aimed to explore the potential association between the LS7 factors and infertility.

Methods

A cross-sectional study was conducted on a sample of 3537 women aged 18-44 years from the National Health and Nutrition Examination Survey (NHANES) spanning the years 2013-2018. The LS7 metrics encompassed various factors including physical activity, smoking habits, body mass index, blood pressure levels, dietary patterns, blood glucose levels, and total cholesterol levels. We computed a 14-point LS7 score based on participants' baseline data, classifying them as "inadequate" (3-6), "average" (7-10), or "ideal" (11-14). Infertility is defined as an affirmative answer to either of two questions on the NHANES questionnaire: "Have you tried to conceive for at least one year without success?" and "Have you sought medical help for your inability to conceive?" Logistic regression was utilized to estimate odds ratios (O.R.s) and 95% confidence intervals (C.I.s).

Results

In total, 17.66% of participants were classified as individuals who reported experiencing infertility. In the continuous analysis, each one-unit increase in LS7 score was associated with a significantly decreased odds of infertility (OR=0.88 [0.77-0.89]). Analyzing the categorical representation of LS7 score, compared to individuals with poor scores, those with ideal scores exhibited a substantial 58% reduction in the odds of infertility (OR=0.42 [0.26-0.69]). Additionally, the observed interaction suggested that the influence of age on the relationship between LS7 and infertility is not consistent across different age groups (P for interaction < 0.001). Among individuals aged 35 or younger, each unit increase in LS7 score was associated with a substantial 18% (OR=0.82 [0.76-0.89]) decrease in the odds of infertility. However, in the older age group (>35), the association was attenuated and non-significant.

Conclusions

Our research suggests a significant inverse association between LS7 scores and infertility. Age demonstrated a varying impact on this relationship, with a more pronounced impact observed among individuals aged 35 or younger.

Exome-informed formulations of food proteins enhance body growth and feed conversion efficiency in ad libitum-fed mice

Meeting requirements for dietary proteins, especially of essential amino acids (EAAs), is critical for the life-long health of living organisms. However, defining EAA targets for preparing biologically-matched nutrition that satisfies metabolic requirements for protein remains challenging. Previous research has shown the advantages of 'exome matching' in representing the specific requirement of dietary AAs, where the target dietary AA profile was derived from in silico translation of the genome of an organism, specifically responsible for protein expression (the 'exome'). However, past studies have assessed these effects in only one sex, for few parameters (body mass and composition), and have used purified diets in which protein is supplied as a mixture of individual AAs. Here, for the first time, we utilise a computational method to guide the formulation of custom protein blends and test if exome matching can be achieved at the intact protein level, through blending standard protein ingredients, ultimately leading to optimal growth, longevity and reproductive function. Mice were provided ad libitum (ad lib) access to one of the four iso-energetic protein-limited diets, two matched and two mis-matched to the mouse exome target, and fed at a fixed protein energy level of 6.2%. During or following 13-weeks of feeding, the food intake, body growth, composition and reproductive functions were measured. Compared to the two mis-matched diets, male and female animals on the exome-matched diet with protein digestibility correction applied, exhibited significantly improved growth rates and final body mass. The feed conversion efficiency in the same diet was also increased by 62% and 40% over the worst diets for males and females, respectively. Male, not female, exhibited higher accretion of lean body mass with the matched, digestibility-corrected diet. All reproductive function measures in both sexes were comparable among diets, with the exception of testicular daily sperm production in males, which was higher in the two matched diets versus the mis-matched diets. The results collectively demonstrate the pronounced advantages of exome-matching in supporting body growth and improving feed conversion efficiency in both sexes. However, the potential impact of this approach in enhancing fertility needs further investigation.

Association between waist circumference and female infertility in the United States

BACKGROUND

Obesity has significant implications for fertility and reproductive health. However, evidences linking abdominal obesity to female infertility were limited and inconclusive. Our objective was to figure out the potential relationship between waist circumference (WC) and infertility among women of childbearing age in the United States using data from the National Health and Nutrition Examination Survey (NHANES).

METHODS

Our cross-sectional study included 3239 female participants aged 18-45 years. To explore the independent relationship between WC and female infertility, the weighted multivariable logistic regression and smoothed curve fitting were performed. Interaction and subgroup analyzes were then conducted for secondary analysis.

RESULTS

WC was positively associated with female infertility independent of BMI after adjusting for BMI and other potential confounders. In fully adjusted model, for every 1cm increase in waist circumference, the risk of infertility increased by 3% (OR = 1.03, 95% CI: 1.01-1.06). When WC was divided into five equal groups, women in the highest quintile had 2.64 times risk of infertility than that in the lowest quintile (OR = 2.64, 95% CI: 1.31-5.30). Smooth curve fitting revealed a non-linear but positively dose-dependent relationship between WC and female infertility. Furthermore, we found an inverted U-shaped relationship (turning point: 113.5 cm) between WC and female infertility in participants who had moderate recreational activities and a J-shaped relationship (turning point: 103 cm) between WC and female infertility in participants who had deficient recreational activities.

CONCLUSIONS

Waist circumference is a positive predictor of female infertility, independent of BMI. Moderate recreational activities can lower the risk of female infertility associated with abdominal obesity.

Age affects the association between socioeconomic status and infertility: a cross-sectional study

BACKGROUND

Previous studies have shown the interaction between age and socioeconomic status (SES) on the risk of infertility in the UK, but the association is still unclear in the United States. Therefore, the present study investigated the effect of age on the relationship between SES and the risk of infertility in American women.

METHODS

The study included adults who participated in the National Health and Nutrition Examination Survey (NHANES) from 2013 to 2018. The poverty income ratio (PIR) was used to represent the SES of the population. With participants stratified according to age category (< 35 years; ≥ 35 years), we further assessed differences in the relationship between PIR and infertility risk among participants of different age groups using multivariate logistic regression and interaction tests.

RESULTS

Approximately 3,273 participants were enrolled in the study. There were 399 cases of infertility and 2,874 cases without infertility. In women ≥ 35 years of age, PIR levels were significantly higher in infertile participants than in non-infertile participants, but no such difference was found in those < 35 years of age. The association of PIR with the risk of infertility appeared to differ between age < 35 years and age ≥ 35 years (OR: 0.99, 95%Cl: 0.86-1.13 vs. OR: 1.24, 95%Cl: 1.12-1.39) in a fully adjusted model. Furthermore, an interaction between age and PIR increased the risk of infertility (p-value for interaction < 0.001).

CONCLUSION

Our study found that age may influence the association between PIR and infertility. It is imperative to perform further studies to provide more evidence.

The association between weight-adjusted-waist index and self-reported infertility among women of reproductive age in the United States

AIM

This study aimed to determine whether the weight-adjusted-waist index (WWI) affected infertility in women of childbearing age in the United States.

METHODS

In this study, a database from the 2013 to 2018 National Health and Nutrition Examination Survey (NHANES) was used. We analyzed 3374 participants' data cross-sectionally. The survey used WWI and fertility status as independent and dependent variables. To determine the effect of WWI, an analysis of the independent relationship between WWI and infertility was conducted using weighted multivariable logistic regression and a generalized additive mode (GAM). A smooth curve fitting test was used to calculate whether there was a linear association between WWI and the incidence rate of infertility, as well as subgroup analyses and interaction tests.

RESULTS

The prevalence of infertility was 10.19% among 3374 participants. Higher WWI quartiles were associated with higher infertility rates. Based on a fully adjusted model, the effects of WWI on fertility were positive (odds ratio = 1.39, 95% confidence interval: 1.17-1.66). As a result of smooth curve fitting, the association was linear across the entire WWI. Different characteristics were associated with different risks of infertility in subgroup analysis.

CONCLUSION

Among women of reproductive age in the United States, WWI levels were positively associated with infertility. This relationship needs to be confirmed by further studies.

Body Fat Distribution and Female Infertility: a Cross-Sectional Analysis Among US Women

At present, the effect of body fat distribution on female reproductive health is still inconclusive. The purpose of our study was to analyze the correlation between female infertility rates and the fat mass portion of the android region to the gynoid region (the A/G ratio) among US women of reproductive age. Female infertility is defined as a failure to get pregnant after 12 months of unprotected sexual activity. A total of 3434 women of reproductive age were included in this study as part of the 2013-2018 National Health and Nutrition Examination Survey (NHANES). The A/G ratio was used to assess the body fat distribution of participants. Based on the comprehensive study design and sample weights, it was determined that the A/G ratio was associated with female infertility primarily through logistic regression analyses. After adjusting for potential confounders, the multivariate regression analysis indicated an increase in the A/G ratio was correlated with an increase in the prevalence of female infertility (OR = 4.374, 95% CI:1.809-10.575). Subgroup analyses showed an increased prevalence of infertility in non-Hispanic Whites (P = 0.012), non-diabetic individuals (P = 0.008), individuals under 35 years old (P = 0.002), and individuals with secondary infertility (P = 0.01). The trend tests and smooth curve fitting illustrate a linear trend between the A/G ratio and female infertility. Future researches are warranted to confirm the causal relationship between body fat distribution and female infertility, which may provide an insight into future prevention and treatment of female infertility.

Association between different insulin resistance surrogates and infertility in reproductive-aged females

BACKGROUND

Obesity and metabolic syndrome are observed more frequently in infertile women, and insulin resistance (IR) is closely related to them. However, there are no studies that have examined the association between different IR surrogates and female infertility, hence we investigated the potential association between them in the general population.

METHODS

This was a cross-sectional study using data from the National Health and Nutrition Examination Survey (NHANES, 2013-2018). The association of different IR surrogates (HOMA-IR index, TyG index and TyG-BMI index) with female infertility was estimated by multivariable regression analysis.

RESULTS

After adjusting for confounders, the HOMA-IR index and TyG index did not show an association with female infertility, while the TyG-BMI index was found to have a positive association with female infertility (OR = 1.01, 95% CI: 1.00, 1.01; P < 0.0001), and the OR of the TyG-BMI group T3 (≥ 255.55) was significantly different compared to the group T1 (< 185.31) (OR = 3.02, 95% CI: 1.62, 5.60). Similar results were seen in most of the subgroup participants by stratified analysis (P-interaction > 0.05). However, different IR surrogates did not show variability in their ability to predict infertility [TyG-BMI: 0.68 (95% CI: 0.62, 0.74) vs. TyG: 0.62 (95% CI: 0.57, 0.68) vs. HOMA-IR: 0.65 (95% CI: 0.60, 0.71)].

CONCLUSIONS

Our result suggests that high levels of TyG-BMI index were positively associated with female infertility in US reproductive-aged females.

Endocrine factors associated with infertility in women: an updated review

INTRODUCTION

Infertility is defined as the inability to conceive after unprotected sexual intercourse for at least 12 consecutive months. Our objective is to present an updated narrative review on the endocrine causes of infertility in women.

AREAS COVERED

A comprehensive review was conducted using Scielo, Scopus, and EMBASE databases, comprising 245 articles. The pathophysiology of infertility in women was described, including endocrinopathies such as hypothalamic amenorrhea, hyperprolactinemia, polycystic ovary syndrome, primary ovarian insufficiency, obesity, thyroid dysfunction, and adrenal disorders. The diagnostic approach was outlined, emphasizing the necessity of hormonal studies and ovarian response assessments. Additionally, the treatment plan was presented, commencing with non-pharmacological interventions, encompassing the adoption of a Mediterranean diet, vitamin supplementation, moderate exercise, and maintaining a healthy weight. Subsequently, pharmacological treatment was discussed, focusing on the management of associated endocrine disorders and ovulatory dysfunction.

EXPERT OPINION

This comprehensive review highlights the impact of endocrine disorders on fertility in women, providing diagnostic and therapeutic algorithms. Despite remaining knowledge gaps that hinder more effective treatments, ongoing research and advancements show promise for improved fertility success rates within the next five years. Enhanced comprehension of the pathophysiology behind endocrine causes and the progress in genetic research will facilitate the delivery of personalized treatments, thus enhancing fertility rates.

Association between weight-adjusted-waist index and female infertility: a population-based study

Aims

Obesity is detrimental to infertility. The association between weight-adjusted-waist index (WWI, a recently developed adiposity indicator) and infertility has not previously been confirmed.

Methods

The data for this study were obtained from the National Health and Nutrition Examination Survey (NHANES) 2013-2018. Each participant's WWI was calculated as their waist circumference in centimeters by the square root of weight in kilograms. Multivariable logistic regression and generalized additive model were utilized to investigate the relationship between WWI with infertility. We used smoothed curve fitting to explore the non-linear relationship. Subgroup analysis and interaction tests were also conducted.

Results

A total of 3,526 participants with ages from18 to 45 were enrolled, 364 of whom were infertile. With the higher WWI, infertility was more prevalent (OR = 1.42, 95% CI: 1.22-1.65), and this association was still consistent in subgroups (all P for interaction> 0.05). Smoothed curve fitting showed a positive non-linear relationship between WWI and infertility. Furthermore, we discovered that WWI had a stronger connection with the risk of infertility than other markers of obesity including WC, body mass index (BMI) and a body shape index (ABSI).

Conclusions

Weight-adjusted-waist index levels were positively linked to an increased risk of infertility in American females and showed a stronger association than other markers of obesity. Our research indicated WWI could help identify women with infertility, and managing obesity as determined by WWI may help to reduce the risk of infertility.

Protective effect of Salvia hispanica (chia seeds) against obesity induced ovarian disorders in rat model

The main goal of the current report is to assess the protective impacts of chia seeds against obesity-induced ovarian dysfunctions with a trial to elucidate the mechanism of action. Forty rats were divided into 4 groups including lean untreated, lean consuming chia seeds, obese untreated, and rats consumed high-fat diet (HFD) mixed with ground chia seeds for 10 weeks. Anthropometric measures including visceral fat, peri-ovarian fat, ovarian weights, and duration of the estrous cycle were computed. Serum luteinizing (LH), follicular stimulating (FSH), progesterone, estradiol hormones, and tumor necrosis-α (TNF-α) were estimated. Ovarian histopathology and immunohistochemistry (CD31) were performed. Results showed that chia seeds clearly reduced obesity and induced alteration in anthropometric measures with a clear increase in LH and progesterone. Such seeds notably reversed histopathological alteration and reduced TNF-α, and CD31 induced by HFD. Conclusively, chia seeds have a potential protective role against obesity-induced ovarian dysfunction owing to their anti-inflammatory properties.

Weight Bias in Reproductive Medicine: A Curiously Unexplored Frontier

Obesity has been associated with a multitude of medical comorbidities, infertility, and adverse obstetric outcomes. Weight stigma and weight bias pervade not only the medical field but also education, employment, and activities of daily living. The experience of weight stigma has been shown to adversely impact not only the mental health of individuals with overweight or obesity but also worsen obesogenic behaviors, and medical comorbidities. This review frames the rise of weight stigma and weight bias within the context of the "obesity epidemic" and explores its associations with infertility and decreased access to health care and its subsequent impact on the lives of individuals. Furthermore, it explores the concepts of intrinsic and extrinsic weight stigma/bias and highlights the need for further examination and research into the impact of these factors on access to reproductive medicine and subsequent outcomes.

The association between aldehydes exposure and female infertility: A cross-sectional study from NHANES

Environmental pollutants could be implicated in the cause of female infertility beyond traditional factors. Until now, no study has focused on the association of environmental exposure to aldehydes with female infertility. This study intended to investigate the possible impact of serum levels of aldehyde on female infertility. A cross-sectional study was performed on 516 nationally representative participants from 2013 to 2014 National Health and Nutrition Examination Survey (NHANES) in US. Multivariate logistic regression models and restricted cubic splines were used to examine the association between serum levels of aldehydes and the risk of female infertility. Women in the highest tertile of exposure to benzaldehyde had a 66% (odds ratio [OR] = 0.34, 95% confidence interval [CI] = 0.14-0.79) lower risk of infertility compared to those in the lowest tertile, after adjusting for other variables. Restricted cubic spline indicated a linear and negative association of benzaldehyde with female infertility (p for nonlinearity = 0.74), while other aldehydes did not exhibit a significant correlation. In summary, this cross-sectional study indicates that higher benzaldehyde level correlated with a lower rate of female infertility, which could help guide future research and contribute to the development of interventions to prevent or treat infertility and improve reproductive health outcomes.

Association of undernutrition and female infertility in East Africa: Finding from multi-country demographic and health surveys

Introduction

Infertility is one of the public health problems affecting a significant number of women in the reproductive age group. Although female fertility is predominantly affected by gynecological and systemic diseases, lifestyle and nutritional factors also play an important role in secondary female infertility. Therefore, this study aimed to determine the pooled prevalence of secondary female infertility and its association with undernutrition using nationwide data from the Demographic and Health Surveys (DHS) of eastern African countries.

Methods

The data of ten East African countries that comprise a weighted sample of 38,020 women data were accessed from measure DHS. Data processing and analysis were performed using STATA 15 software. A multilevel mixed-effect logistic regression model was fitted to examine the association between undernutrition and secondary infertility. Variables with a p-value < 0.05 were declared as significant factors associated with secondary infertility. Model comparison was done based on Akaike and Bayesian Information Criteria (AIC and BIC). To measure variation (random effects), Community-level variance with standard deviation and intra-cluster correlation coefficient (ICC) was used.

Result

The proportion of women who have secondary infertility was 16.32% with 95%CI (15.96, 16.69), of which 26.94% were undernourished. This study found that being undernutrition (AOR = 1.74; 95%CI: 1.54-1.98) and overweight (AOR = 1.72; 95%CI: 1.62-1.86) were significantly associated with secondary infertility. Women aged >35 years (AOR = 3.47; 95%CI: 2.66-4.55), and rural residents (AOR = 1.16; 95%CI: 1.02-1.37) are other factors that are positively associated with secondary infertility. However, primary education (AOR = 0.87; 95%CI: 0.77-0.97) and richer wealth index (AOR = 0.84; 95%CI: 0.73-0.97) are protective factors for secondary infertility.

Conclusion

This study indicated that there is a strong association between secondary infertility and undernutrition growing in Eastern Africa. Therefore, Health information dissemination and awareness creation on the impact of malnutrition on infertility should be given to the community and health care providers. Given this, it may lead to integrating nutrition counseling into both clinical settings for infertility management as well as national dietary guidelines for individuals of reproductive age.

The association between dietary selenium intake and Hashimoto's thyroiditis among US adults: National Health and Nutrition Examination Survey (NHANES), 2007-2012

BACKGROUND

Selenium has been shown to influence the pathological processes and physiological functions of thyroid. Although growing evidence has shown that selenium can improve the treatment of Hashimoto's thyroiditis (HT), there is a need to evaluate the association between dietary selenium intake and HT in a large cross-sectional study. This study explored the association between dietary selenium intake and HT based on the National Health reand Nutrition Examination Survey (NHANES) database (2007-2012).

METHODS

A total of 8756 of 30,442 participants were included in the study. Dietary selenium intake was the independent variable, while HT was the dependent variable. In addition, the relative importance of the selected variables was determined using the XGBoost model. A smooth curve was constructed based on the fully adjusted model to investigate the potential linear relationship between dietary selenium intake and HT. Smooth curves were also constructed to explore the linear/non-linear relationship between dietary selenium intake and thyroid peroxidase antibody (TPOAb)/ thyroglobulin antibody (TgAb).

RESULTS

The mean age of the enrolled participants was 44.35 years (± 20.92). The risk of HT was significantly reduced by a 35% per-unit increase in dietary selenium intake after fully adjusting for covariates according to the model (log2-transformed data; OR 0.65; 95% CI 0.51, 0.83). The XGBoost model revealed that dietary selenium intake was the most important variable associated with Hashimoto's thyroiditis. Dietary selenium intake (Log2-transformed) was negatively correlated with TPOAb levels [- 16.42 (- 22.18, - 10.65), P < 0.0001], while a non-linear relationship was observed between dietary selenium intake and TgAb with an inflection point of 6.58 (95.67 μg, Log2-transformed).

CONCLUSION

Dietary selenium intake is independently and inversely associated with HT risk. Moreover, dietary selenium intake is negatively correlated with TPOAb levels and non-linearly correlated with TGAb levels. Therefore, dietary selenium intake may be a safe and low-cost alternative for the prevention and treatment of HT.

Obesity: A Doorway to a Molecular Path Leading to Infertility

The dramatic rise in obesity has recently made it a global health issue. About 1.9 billion were overweight, and 650 million global populations were obese in 2016. Obese women suffer longer conception time, lowered fertility rates, and greater rates of miscarriage. Obesity alters hormones such as adiponectin and leptin, affecting all levels within the hypothalamic-pituitary-gonadal axis. Advanced glycation end products (AGEs) and monocyte chemotactic protein-1 (MCP-1) are inflammatory cytokines that may play an important role in the pathophysiology of ovarian dysfunction in obesity. In obese males, there are altered sperm parameters, reduced testosterone, increased estradiol, hypogonadism, and epigenetic modifications transmitted to offspring. The focus of this article is on the possible adverse effects on reproductive health resulting from obesity and sheds light on different molecular pathways linking obesity with infertility in both female and male subjects. Electronic databases such as Google Scholar, Embase, Science Direct, PubMed, and Google Search Engine were utilized to find obesity and infertility-related papers. The search strategy is detailed in the method section. Even though multiple research work has shown that obesity impacts fertility in both male and female negatively, it is significant to perform extensive research on the molecular mechanisms that link obesity to infertility. This is to find therapeutics that may be developed aiming at these mechanisms to manage and prevent the negative effects of obesity on the reproductive system.

Adipokinesand Ghrelin Rolein Regulation of Ovarian Function in Obesity

There is a great worldwide trend in the incidence of obesity, which is increasing with each passing year among all populations, including women of reproductive age. Given the impressive list of diseases associated with obesity, as well as the negative inverse correlation of the severity of obesity with fertility, this problem is global not only in the social sphere, but it also becomes demographically significant.

Along with other pathogenetic mechanisms leading to persistent anovulation, an imbalance in adipokine production by adipose tissue can also serve as one of the important links in the development of reproductive dysfunction. Despite apparent interest in this topic, a large number of previously discovered adipokines are still not studied. Among adipokines, the effects of adiponectin and leptin on reproductive function are best known. Alterations in adiponectin and leptin levels can affect hypothalamic-pituitary-gonadal signaling, folliculogenesis, oogenesis and steroidogenesis. In addition, leptin is involved in the initiation of puberty, regulation of the menstrual cycle, and changes the balance between proliferation and apoptosis in ovarian cells. The leading causes of reduced fertility, infertility, and IVF failure in obese patients are mechanisms that promote the formation of chronic anovulation, delay the maturation of oocytes, reduce their quality, and/or lead to changes in endometrial susceptibility. These effects can be caused by an imbalance in the concentrations of leptin and adiponectin (leptin excess and adiponectin deficiency), lead to endometrial dysfunction, disruption of implantation and early embryogenesis. These changes, in turn, can affect just as the likelihood of spontaneous conception, so the effectiveness of assisted reproductive technologies and subsequent gestation.

Thus, the study of potential pathogenetic pathways of fertility regulation in obesity, one of which is the subject of this review, is an important area for further study.