Urinary Phytoestrogens and Relationship to Menstrual Cycle Length and Variability Among Healthy, Eumenorrheic Women

Long-Term Exposure to Isoflavones Alters the Hormonal Steroid Homeostasis-Impairing Reproductive Function in Adult Male Wistar Rats

The consumption of isoflavones is gaining popularity worldwide due to their beneficial effects on health. However, isoflavones are considered to be endocrine disruptors and cause deleterious effects on hormone-sensitive organs, especially in males. Therefore, this study aimed to determine if a continuous and prolonged exposure to isoflavones in adult males altered the endocrine axis effect of testicular function. For this purpose, seventy-five adult male rats were administered with low and high mixtures of isoflavones (genistein and daidzein) for 5 months. The determination of steroid hormones (progesterone, androstenedione, dehydroepiandrosterone, testosterone, dihydrotestosterone, 17β-estradiol, and estrone sulphate) was carried out in serum and testicular homogenate samples. Sperm quality parameters and testicular histology were also determined. The results revealed that low and high doses of isoflavones promote a hormonal imbalance in androgen and estrogen production, resulting in a decrease in circulating and testicular androgen levels and an increase in estrogen levels. These results are associated with a reduction in the sperm quality parameters and a reduction in the testicular weight, both in the diameter of the seminiferous tubules and the height of the germinal epithelium. Altogether, these results suggest that a continuous exposure to isoflavones in adult male rats causes a hormonal imbalance in the testes that disrupts the endocrine axis, causing defects in testicular function.

The effects of flaxseed or its oil supplementations on polycystic ovary syndrome: A systematic review of clinical trials

Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders around the world that can endanger reproductive, metabolic, and psychological health in women. Flaxseed is considered as a functional food which provides remarkable amounts of α-linolenic acid (ALA), phytosterogenic lignans, and dietary fibers. This study aimed to investigate the effectiveness of flaxseed or its oil supplementation on PCOS patients. We systematically searched all published randomized clinical trials indexed in PubMed, Scopus, and Google Scholar databases from inception up to May 2022. Intended exposure and outcome were flaxseed or its oil and metabolic, anthropometric, and hormonal status of women with PCOS, respectively. Initial search via related keywords revealed 69 articles. After excluding duplicates, title and abstract of 55 remaining papers were screened. Fourteen papers were obtained for full text screening. Finally, nine clinical trials published between 2011 and 2021 were included in qualitative synthesis. Based on the results of the present systematic review, we suggest that flaxseed supplementation has the potential to improve metabolic, hormonal, and anthropometric parameters in women with PCOS. However, we also deduce that due to the scarcity of high-quality studies, additional studies need to be conducted in order to derive a solid conclusion.

The role of soy and soy isoflavones on women's fertility and related outcomes: an update

Soy is a key food in human nutrition. It is widely used in eastern traditional cuisine and it has recently diffused among self-conscious and vegetarian diets. The success of soy mainly depends on versatility and supposed healthy properties of soy foods and soy components. Meanwhile, the possible influence on endocrine system, in particular by isoflavones, raised concerns among some researchers. The present paper aims to conduct a review of available data on the effect of soy, soy foods and soy components on women's fertility and related outcomes. Eleven interventional studies, eleven observational studies and one meta-analysis have been selected from the results of queries. A weak, not clinically relevant effect has been highlighted on cycle length and hormonal status. However, a suggestive positive influence has been shown among women with fertility issues and during assisted reproductive technologies. Overall, soy and soy components consumption do not seem to perturb healthy women's fertility and can have a favourable effect among subjects seeking pregnancy. However, because of the paucity of studies exploring the impact of soy intake on women's fertility, as well as the limited population sample size, the frequently incomplete specimens’ collection to investigate all cycle phases and the insufficient characterisation of participants, the evidence is suggestive and it needs further in-depth research taking into account all these aspects.

Genistein affects gonadotrophin-releasing hormone secretion in GT1-7 cells via modulating kisspeptin receptor and key regulators

Epidemiological studies have shown that genistein, an isoflavonoid phytoestrogen from soybean, affects endocrine and reproductive systems and alters pubertal onset. Administration of genistein in mice could impact the electrophysiology of hypothalamic neurons associated with the secretion of gonadotropin-releasing hormone (GnRH), a key component of hypothalamic-pituitary-gonadal (HPG) axis that governs hormone release and reproductive maturation. However, whether genistein could directly influence GnRH secretion in GnRH-specific neurons requires further investigation. Here, mouse hypothalamic GT1-7 neurons were recruited as a GnRH-expressing model to directly evaluate the effect and mechanisms of genistein on GnRH release. Results from this study demonstrated that genistein treatment decreased cell viability, impacted cell cycle distribution, and induced apoptosis of GT1-7 cells. A high concentration of genistein (20 μM) significantly increased GnRH secretion by 122.4% compared to the control. Since GnRH release is regulated by components of the kisspeptin-neurokinin-dynorphin (KNDy) system and regulators including SIRT1, PKC_γ, and MKRN3, their transcription and translation were examined. Significant increases were observed for the mRNA and protein levels of the KNDy component kisspeptin receptor (Gpr54/Kissr). Compared to the control, genistein treatment upregulated the level of Sirt1 mRNA level, while it downregulated Prkcg and Mkrn3 expression. Therefore, this study provided direct evidence that genistein treatment could affect GnRH secretion by modulating kisspeptin receptors, SIRT1, PKC_γ and MKRN3 in GT1-7 cells.Abbreviations: GnRH: gonadotropin-releasing hormone; HPG: hypothalamic-pituitary-gonadal; KNDy: kisspeptin-neurokinin-dynorphin; LH: luteinizing hormone; FSH: follicle-stimulating hormone; ARC: arcuate nucleus; ER: estrogen receptor; SIRT1: silent information regulator 1; PKCγ: protein kinase c γ: MKRN3: makorin ring finger protein 3; LC: lethal concentration; PI: propidium iodide; ECL: chemiluminescence; BCA: bicinchoninic acid assay; PBS: phosphate-buffered saline; CT: fluorescence reached threshold; PVDF: polyvinylidene difluoride.

Menstrual cycle length and modern living: a review

PURPOSE OF REVIEW

The aim of this review is to evaluate biological, life history, environmental, and lifestyle factors and exposures that cause variability in menstrual cycle length (MCL).

RECENT FINDINGS

Recent literature has detailed a number of factors that influence MCL, with particular emphasis placed on novel environmental exposures, such as air pollution and endocrine disrupting chemicals.

SUMMARY

MCL varies widely in response to intrinsic and extrinsic inputs and is a useful predictor of reproductive health and fecundability.

VIDEO ABSTRACT

http://links.lww.com/COE/A28.

Lignan exposure: a worldwide perspective

Dietary lignans are phytoestrogens that are mostly found in plant-based foods, especially whole grains, seeds, nuts, legumes and vegetables. An accurate assessment of lignan exposure is crucial to evaluate their potential health benefits and to establish future recommendations and dietary guidelines. This narrative review aimed to (i) summarize the pros and the cons of the current main assessment methods for lignan exposure─i.e., dietary questionnaires, food composition tables and biomarkers, (ii) describe the individual lignans more consumed from a worldwide perspective, as well as their main food sources, (iii) determine the lignans concentrations in both urine and blood, and explore their heterogeneity among countries, and finally (iv) discuss the main determinants of lignan exposure.

Neither soyfoods nor isoflavones warrant classification as endocrine disruptors: a technical review of the observational and clinical data

Soybeans are a rich source of isoflavones, which are classified as phytoestrogens. Despite numerous proposed benefits, isoflavones are often classified as endocrine disruptors, based primarily on animal studies. However, there are ample human data regarding the health effects of isoflavones. We conducted a technical review, systematically searching Medline, EMBASE, and the Cochrane Library (from inception through January 2021). We included clinical studies, observational studies, and systematic reviews and meta-analyses (SRMA) that examined the relationship between soy and/or isoflavone intake and endocrine-related endpoints. 417 reports (229 observational studies, 157 clinical studies and 32 SRMAs) met our eligibility criteria. The available evidence indicates that isoflavone intake does not adversely affect thyroid function. Adverse effects are also not seen on breast or endometrial tissue or estrogen levels in women, or testosterone or estrogen levels, or sperm or semen parameters in men. Although menstrual cycle length may be slightly increased, ovulation is not prevented. Limited insight could be gained about possible impacts of in utero isoflavone exposure, but the existing data are reassuring. Adverse effects of isoflavone intake were not identified in children, but limited research has been conducted. After extensive review, the evidence does not support classifying isoflavones as endocrine disruptors.