Roles of Vitamin D in Reproductive Systems and Assisted Reproductive Technology

Menstrual Blood as a Non-Invasive Alternative for Monitoring Vitamin Levels

Background/Objectives: Menstrual blood has recently emerged as a novel specimen for diagnostics, offering a non-invasive alternative to traditional blood testing methods. Despite the importance of vitamins and monitoring their levels in preventative healthcare measures, the feasibility of measuring them in menstrual blood has yet to be explored. In this study, we aimed to assess the potential of using menstrual blood for determining vitamin levels by comparing their levels in menstrual blood to those in matched capillary blood samples. Methods: A prospective, monocentric, observational study was conducted with healthy, reproductive-aged voluntary participants. Menstrual blood was collected from 30 participants using a menstrual cup, and the corresponding capillary blood samples were obtained using a finger prick. The samples were transferred to dried blood spot (DBS) cards and analyzed using mass spectrometry to determine vitamin levels. Statistical analyses were performed to compare menstrual blood vitamin A and D levels, and hemoglobin, to those in capillary blood. Results: The vitamin levels could be ascertained from the menstrual blood, and were observed to significantly correlate with those from the capillary blood for both vitamin A (r = 0.77, p < 0.001) and vitamin D (r = 0.66, p < 0.001), despite being statistically different. Conclusions: The results of this pilot study demonstrate the potential utility of menstrual blood in estimating vitamin A and D levels, illustrating the prospect of a non-invasive menstrual blood-based vitamin test following larger clinical and analytical validation studies.

Vitamin D levels in couples undergoing in vitro fertilization treatment: lack of association with embryo quality or pregnancy rates

OBJECTIVE

To investigate the potential impact of vitamin D (VD) serum levels on couples going through in vitro fertilization treatment in terms of embryo quality and pregnancy rates.

DESIGN

A retrospective cohort study.

SETTING

A private human reproduction center.

PATIENT(S)

A total of 267 couples underwent intracytoplasmic sperm injections between January 2017 and March 2019.

INTERVENTION(S)

The couples were categorized into four groups on the basis of 25-hydroxy VD (25OHD) levels measured at the beginning of the stimulation protocol: group 1 with 25OHD levels ≥30 ng/mL for both women and men; group 2 with 25OHD levels <30 ng/mL for both; group 3 women with 25OHD levels <30 ng/mL and men with 25OHD levels ≥30 ng/mL; and group 4 with women with 25OHD level ≥30 ng/mL and men with 25OHD level <30 ng/mL.

MAIN OUTCOME MEASURE(S)

We consider the quantity and quality of embryos during the cleavage as well as blastocyst stages as primary outcomes. Correspondingly, the clinical pregnancy rate (CPR) was regarded as a secondary outcome.

RESULT(S)

Our findings revealed no significant correlations between the studied VD groups and the evaluated outcomes. This includes the quantity and quality of embryos during the cleavage and blastocyst stages, as well as the CPR. Primary analysis revealed a small but statistically significant difference in the duration of controlled ovarian stimulation between group 1 and group 2 (95% confidence interval, 0.07-3.04) and between group 1 and group 3 (95% confidence interval, 0.05-3.23).

CONCLUSION(S)

The present study found no correlation between the studied VD levels and the quantity as well as quality of cleavage or blastocyst stage embryos, nor did it show any impact on CPRs. Further well-designed, prospective studies are warranted to determine whether and how vitamin D affects reproductive outcomes.

The causal relationship between hydatidiform mole and nutrients: A two-sample Mendelian randomization study

BACKGROUND

Hydatidiform mole (HM), a subset of gestational trophoblastic disease, is considered precancerous and exhibits geographical variation. The incidence of HM is linked to nutritional factors. This study aimed to investigate the causal relationship between nutrients and HM using a bidirectional two-sample Mendelian randomization (MR) approach.

METHODS

We utilized publicly available genome-wide association study data to assess the causal associations between levels of specific vitamins (retinol, vitamins B12, B6, C, D, E, folate, and carotene) and minerals (iron, calcium, and magnesium) with HM. The MR analysis was conducted and reported following the STROBE-MR guidelines, employing MR Egger and inverse variance weighted (IVW) methods to estimate associations, with MR-PRESSO for pleiotropy testing.

RESULTS

The study revealed vitamin B6 as a significant protective factor against HM (MR-Egger OR: 0.094, 95 % CI: 0.011-0.0778, P < 0.05; IVW OR: 0.365, 95 % CI: 0.142-0.936, P < 0.05). Folate and magnesium showed suggestive associations with HM, whereas most other nutrients did not exhibit a causal relationship. MR-PRESSO analysis supported the absence of horizontal pleiotropy of vitamin B6. Besides, reverse MR analysis did not reveal a significant causal association between HM and serum nutrient levels, suggesting that differences of nutrients in HM patients may not be directly attributed to the mole.

CONCLUSION

This MR study provides evidence that vitamin B6 may protect against HM, and suggests potential roles for folate and magnesium in HM development, while highlighting the need for further research to confirm these findings.

Relationship between serum vitamin D concentration and parameters of gonadal function in infertile male patients

Background

Vitamin D (vitD) deficiency could affect male reproductive function. Our objective was to investigate the relationship between serum vitD concentrations and hormonal and seminal parameters in infertile patients and to compare the results with those in healthy controls.

Materials and methods

Infertile patients (n = 29) and normozoospermic healthy donors (n = 27) were recruited for the study. Serum concentrations of vitD, total testosterone, estradiol, and sex hormone-binding globulin were determined using chemiluminescence assays, and free testosterone concentration was determined by radioimmunoassay. Semen analysis was performed as suggested by the World Health Organization. Statistical analysis was conducted using Student's t test, contingency tables, and linear regression studies.

Results

VitD concentrations were lower in patients than in controls (p < 0.001). A significant association (p < 0.001) was observed between vitD concentrations <20ng/mL and infertility. In the control group, significant correlations were reported between vitD concentrations >30 ng/mL and the concentrations of testosterone (p < 0.05), free testosterone (p < 0.01), and estradiol (p < 0.05). A direct correlation was found between vitD concentration and percentage of sperm vitality (p = 0.01). VitD also positively correlated with the percentage of progressive sperm motility (p <0.05) and sex hormone-binding globulin concentrations (p < 0.01).

Conclusions

VitD may affect male reproductive parameters, and its deficiency could be associated with infertility.

The effects of supplementation of vitamin D to the egg-yolk extender on cryopreservation of ram semen

OBJECTIVES

This study aimed to examine the effects of supplementation of vitamin D to the egg-yolk extender on characteristics of frozen-thawed ram semen.

METHODS

Semen samples obtained from adult rams were pooled and divided into five equal volumes. It was reconstituted with extenders containing different concentrations of vitamin D: 0 (control), 12.5 (VITD 12.5), 25 (VITD 25), 50 (VITD 50), and 100 ng/mL (VITD 100), and then they were frozen. Sperm motility parameters, plasma membrane functional integrity, acrosomal integrity, DNA fragmentation, and mitochondrial membrane potential of the groups were evaluated after sperm thawing.

RESULTS

Total motility and progressive motility were higher in VITD 50 than in all other groups (p < 0.05). Higher sperm straightness, linearity, and wooble were higher in VITD 50 than in the control group (p < 0.05). A similar pattern of VITD 50 was observed for plasma membrane integrity and mitochondrial membrane potential (p > 0.05).

CONCLUSIONS

In the study, it was observed that adding vitamin D to the extender had a beneficial effect on ram spermatological parameters. In addition, it was concluded that the use of the 50 ng/mL vitamin D in the extender provided more effective protection than the other doses.

Vitamin D and reproductive disorders: a comprehensive review with a focus on endometriosis

Vitamin D is a fat-soluble steroid hormone that was initially known only for regulating calcium and phosphorus levels and maintaining bone health. However, it was later discovered that many organs express vitamin D metabolizing enzymes and have a ligand for vitamin D, which regulates the expression of an extensive assortment of genes. As a result, vitamin D is indispensable for the proper function of organs, and its deficiency is believed to be a critical factor in symptoms and disorders such as cardiovascular diseases, autoimmune diseases, and cancers. The significance of vitamin D in reproductive tissues was recognized later, and studies have revealed its crucial role in male and female fertility, as well as proper reproductive function during pregnancy. Vitamin D deficiency has been identified as a risk factor for infertility, gonadal cancers, pregnancy complications, polycystic ovary syndrome, and endometriosis. However, data investigating the association between vitamin D levels and reproductive disorders, including endometriosis, have encountered inconsistencies. Therefore, the present study aims to review existing research on the effect of vitamin D on proper reproductive function, and the role of deficiency in reproductive diseases and specifically focuses on endometriosis.

D-hormone and its significance for function of prostate gland (literature review and personal observations)

OBJECTIVE

Aim: The aim of this article is to present literature data and personal research of the role of D-hormoneon the functioning of the male reproductive system, and more specifically of the prostate gland, as well as the use of this vitamin D during the complex and independent treatment of benign prostatic hyperplasia in preclinical studies and clinical practice.

PATIENTS AND METHODS

Materials and Methods: The collection of relevant data were done using the scientific databases Pubmed, Google Scholar. A manual search on reproductive endocrinology and pharmacology sources were also conducted for related published studies . Selected keywords ("benign prostatic hyperplasia" OR "BPH") AND ("prostate") AND ("reproductive system and vitamin D") were used to collect data. The article also presents our personal data of preclinical studies and clinical data of the use of vitamin D as monotherapy and in the complex therapy of reproductive disorders.

CONCLUSION

Conclusions: The effect of vitamin D on prostate volume and BPH has shown perspective results, therefore, it is proposed to conduct further studies on the role of vitamin D in the formation of BPH and reproductive disorders, their prevention and treatment. The use of vitamin D as monotherapy or in the form of pharmaceutical compositions and its inclusion in basic treatment regimens can increase the effectiveness of the prevention and correction of reproductopathies in the presence of or due to BPH and suggests the possibility of restoring the generative potential of individuals with BPH, both with and without D-hypovitaminosis.

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.

Impact of thyroid autoimmunity and vitamin D on in vitro fertilization/intracytoplasmic sperm injection outcomes among women with normal thyroid function

This prospective cohort study aimed to determine the impact of thyroid autoimmunity and total 25-hydroxyvitamin D concentration on early pregnancy outcomes in women undergoing in vitro fertilization/intracytoplasmic sperm injection who had intact thyroid function. The study included 1,297 women who underwent in vitro fertilization/intracytoplasmic sperm injection cycles, although only 588 patients received fresh embryo transfer. The study endpoints were clinical pregnancy, ongoing pregnancy, ectopic pregnancy, and early miscarriage rates. Our study found that the total 25-hydroxyvitamin D serum concentrations (P<0.001) and anti-Mullerian hormone levels (P=0.019) were lower among patients in the TAI group (n=518) than among those in the non-TAI group (n=779). Additionally, the study population in each group was divided into three subgroups according to the total vitamin D status based on clinical practice guidelines (deficient, <20 ng/mL; insufficient, 21-29 ng/mL; and sufficient, ≥30 ng/mL), TAI group: sufficient, n=144; insufficient, n=187; and deficient, n=187; non-TAI group: sufficient, n=329; insufficient, n=318, and deficient, n=133. In the TAI group, the number of good-quality embryos decreased in patients with vitamin D deficiency (P=0.007). Logistic regression analysis indicated that aging prevented women from achieving clinical (P=0.024) and ongoing pregnancy (P=0.026). The current findings suggest that patients with TAI had reduced serum vitamin D concentration. Furthermore, in the TAI group, the number of good-quality embryos decreased in patients with vitamin D deficiency. Finally, aging adversely impacted achieving clinical and ongoing pregnancy.

A parathyroid hormone/salt-inducible kinase signaling axis controls renal vitamin D activation and organismal calcium homeostasis

The renal actions of parathyroid hormone (PTH) promote 1,25-vitamin D generation; however, the signaling mechanisms that control PTH-dependent vitamin D activation remain unknown. Here, we demonstrated that salt-inducible kinases (SIKs) orchestrated renal 1,25-vitamin D production downstream of PTH signaling. PTH inhibited SIK cellular activity by cAMP-dependent PKA phosphorylation. Whole-tissue and single-cell transcriptomics demonstrated that both PTH and pharmacologic SIK inhibitors regulated a vitamin D gene module in the proximal tubule. SIK inhibitors increased 1,25-vitamin D production and renal Cyp27b1 mRNA expression in mice and in human embryonic stem cell-derived kidney organoids. Global- and kidney-specific Sik2/Sik3 mutant mice showed Cyp27b1 upregulation, elevated serum 1,25-vitamin D, and PTH-independent hypercalcemia. The SIK substrate CRTC2 showed PTH and SIK inhibitor-inducible binding to key Cyp27b1 regulatory enhancers in the kidney, which were also required for SIK inhibitors to increase Cyp27b1 in vivo. Finally, in a podocyte injury model of chronic kidney disease-mineral bone disorder (CKD-MBD), SIK inhibitor treatment stimulated renal Cyp27b1 expression and 1,25-vitamin D production. Together, these results demonstrated a PTH/SIK/CRTC signaling axis in the kidney that controls Cyp27b1 expression and 1,25-vitamin D synthesis. These findings indicate that SIK inhibitors might be helpful for stimulation of 1,25-vitamin D production in CKD-MBD.

Impact of nutritional diet therapy on premenstrual syndrome

Premenstrual syndrome (PMS) is one of the most common disorders faced by women of reproductive age. More than 200 symptoms of varying severity associated with PMS have been identified. Because of the broad spectrum of action of PMS and its impact on quality of life, symptom relief is the main challenge of treating PMS and premenstrual dysphoric disorder (PMDD). The review aims to analyze and identify the potential impact of dietary and nutritional therapies on PMS and, respectively, for its better management. The study was conducted by accessing Internet databases such as PubMed, ScienceDirect, and Scopus and using relevant keywords such as PMS, symptoms, dietary patterns (DPs), macro and micronutrients, and supplements. The results showed that diet is an essential modulating factor in reducing and managing PMS symptoms. But research on the actual effect of foods and nutrients on PMS is sparse, sporadic, and studied with insufficient scientific rigor. No correlations were identified between the consumption of macronutrients and PMS: protein, fat, carbohydrates, and fiber, but the effectiveness of micronutrients, especially calcium, magnesium, vitamin D, B vitamins, and herbal supplements, was demonstrated. Researchers remain unanimous that the evidence is insufficient and limited to support their use as an effective treatment. Nevertheless, the results could contribute to providing quality information to help women and girls make evidence-based decisions regarding premenstrual health and the adoption of dietary and nutritional therapies.

Determinants of Dietary Vitamin D Intake in Population-Based Cohort Sample of Polish Female Adolescents

Vitamin D has a pleiotropic effect and its deficiency is a risk factor for many diseases. The purpose of this study was to analyze the dietary intake of vitamin D and the factors determining this intake by female post-primary school students in Poland. The study was conducted on a nationwide sample of 4469 female Polish adolescents (aged 14-20) recruited from all regions across Poland. The vitamin D intake was assessed using VIDEO-FFQ (Vitamin D Estimation Only-Food Frequency Questionnaire). The median dietary vitamin D intake was 2.33 μg per day and it was lower than the 15 μg recommended in Poland for more than 98% of the group. The highest vitamin D intake per day was noted for fish (0.52 μg), whereas the lowest was noted for fats (0.04 μg). Factors that influenced the dietary vitamin D intake were the amount and species of fish consumed, region of residence, use of vitamin D supplements, and vegetarian or vegan diets. In contrast, vitamin D intake did not depend on body mass index and age. Based on the results of the survey, it can be concluded that the alarmingly low intake of vitamin D by Polish female adolescents is a result of the limited supply of vitamin D primarily from fish and fish products. This may be due to insufficient nutritional knowledge, indicating an urgent need to educate the surveyed population in this area.

PCOS Physiopathology and Vitamin D Deficiency: Biological Insights and Perspectives for Treatment

Recent literature has stressed the importance of vitamin D (VD) in polycystic ovary syndrome (PCOS). Women with PCOS are deficient in VD, particularly those with a higher weight. Hypovitaminosis is a risk factor for glucose intolerance, and reduced levels of VD is associated with insulin resistance and increased diabetes risk. Since women with PCOS and hirsutism seem to have lower levels of VD than women with PCOS without hirsutism, a correlation between VD deficiency and hyperandrogenism may be suggested. Interestingly, VD is crucial for many human physiological functions, including to counteract inflammation and oxidative stress. Some studies evaluated effects of VD supplementation on glucose homeostasis variables, hormonal status, lipid concentrations, and biomarkers of inflammation and oxidative stress among VD-deficient women. Moreover, VD has been shown to play a role in egg quality and fertility. This review aims to show the relationship between VD and the endocrine and metabolic profile of PCOS patients, as well as its implications for their fertility. The supplement of VD to the common therapy can lead to an improvement of the insulin resistance and lipid metabolism, a reduction of circulating androgens, as well as a better response to the induction of ovulation in PCOS women.

Female Fertility and the Nutritional Approach: The Most Essential Aspects

Infertility is an increasing problem that affects couples attempting pregnancy. A growing body of evidence points to a link between diet and female fertility. In fact, data show that a diet high in trans fats, refined carbohydrates, and added sugars can negatively affect fertility. Conversely, a diet based on the Mediterranean dietary patterns, i.e., rich in dietary fiber, omega-3 (ɷ-3) fatty acids, plant-based protein, and vitamins and minerals, has a positive impact on female fertility. An unhealthy diet can disrupt microbiota composition, and it is worth investigating whether the composition of the gut microbiota correlates with the frequency of infertility. There is a lack of evidence to exclude gluten from the diet of every woman trying to become pregnant in the absence of celiac disease. Furthermore, there are no data concerning adverse effects of alcohol on female fertility, and caffeine consumption in the recommended amounts also does not seem to affect fertility. On the other hand, phytoestrogens presumably have a positive influence on female fertility. Nevertheless, there are many unanswered questions with regard to supplementation in order to enhance fertility. It has been established that women of childbearing age should supplement folic acid. Moreover, most people experience vitamin D and iodine deficiency; thus, it is vital to control their blood concentrations and consider supplementation if necessary. Therefore, since diet and lifestyle seem to be significant factors influencing fertility, it is valid to expand knowledge in this area.

Single oral dose of vitamin D3 supplementation prior to in vitro fertilization and embryo transfer in normal weight women: the SUNDRO randomized controlled trial

BACKGROUND

Improving in vitro fertilization success is an unmet need. Observational studies have suggested that women with deficient or insufficient vitamin D have lower chances of in vitro fertilization success, but whether supplementation improves clinical pregnancy rate remains unclear.

OBJECTIVE

This study aimed to determine whether oral vitamin D₃ supplementation improves clinical pregnancy in women undergoing an in vitro fertilization cycle.

STUDY DESIGN

The "supplementation of vitamin D and reproductive outcome" trial is a 2-center randomized superiority double-blind placebo-controlled trial. Subjects were recruited between October 2016 and January 2019. Participants were women aged 18 to 39 years with low vitamin D (peripheral 25-hydroxyvitamin D of <30 ng/mL), serum calcium of ≥10.6 mg/dL, body mass index of 18 to 25 kg/m², and antimüllerian hormone levels of >0.5 ng/mL and starting their first, second, or third treatment cycle of conventional in vitro fertilization or intracytoplasmic sperm injection. The primary outcome was the cumulative clinical pregnancy rate per cycle. Pregnancies obtained with both fresh or frozen embryo transfers were included. Clinical pregnancy was defined as an intrauterine gestational sac with a viable fetus. The primary analysis was performed according to the intention-to-treat principle and could also include natural conceptions. Secondary outcomes included total dose of gonadotropins used, embryologic variables (number of oocytes retrieved, number of suitable oocytes retrieved, fertilization rate, and rate of top-quality embryos), and clinical outcomes (miscarriage rate and live birth rate).

RESULTS

Overall, 630 women were randomized 2 to 12 weeks before the initiation of the in vitro fertilization cycle to receive either a single dose of 600,000 IU of vitamin D₃ (n=308) or placebo (n=322). Interestingly, 113 (37%) and 130 (40%) women achieved a clinical pregnancy in the treatment and placebo groups, respectively (P=.37). The risk ratio of clinical pregnancy in women receiving vitamin D₃ was 0.91 (95% confidence interval, 0.75-1.11). Compared with the placebo, vitamin D₃ supplementation did not improve the rate of clinical pregnancy. Exploratory subgroup analyses for body mass index, age, indication to in vitro fertilization, ovarian reserve, interval between drug administration and initiation of the cycle, and basal levels of 25-hydroxyvitamin D failed to highlight any clinical situation that could benefit from the supplementation.

CONCLUSION

In women with normal weight with preserved ovarian reserve and low vitamin D levels undergoing in vitro fertilization cycles, a single oral dose of 600,000 IU of vitamin D₃ did not improve the rate of clinical pregnancy. Although the findings do not support the use of vitamin D₃ supplementation to improve in vitro fertilization success rates, further studies are required to rule out milder but potentially interesting benefits and explore the effectiveness of alternative modalities of supplementation.

Vitamin D, Bone Metabolism, and Fracture Risk in Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder among premenopausal women. PCOS may have reproductive, metabolic, cardiovascular, and psychological implications. Vitamin D deficit is often encountered in PCOS women and may contribute to the pathophysiology of this disorder. As of the key role of vitamin D in bone and mineral metabolism, and because the vitamin D status appears to be closely linked with the PCOS manifestations including insulin resistance, obesity, ovulatory and menstrual irregularities, oxidative stress and PTH elevation, hypovitaminosis D may directly and indirectly via the different facets of PCOS impair bone health in these women. Although limited data are available on life-long fracture risk in women with PCOS, the importance of preserving bone health in youth and adults to prevent osteoporosis and related fractures is also recognized in PCOS women. Evidence of the association between vitamin D and the clinical hallmarks of PCOS are summarized and discussed. Vitamin D arises as a cornerstone in women with PCOS and contributes to the pathophysiological link between PCOS and bone metabolism.

[Vitamin D and reproductive health]

Vitamin D insufficiency and deficiency in women with infertility is more common than in the population. However, we still do not know the exact mechanisms for the participation of vitamin D in the regulation of reproductive function. The purpose of this study is to analyze actual literature data on the role of vitamin D in the regulation of reproductive system and its influence on using of assisted reproductive technologies for the treatment of infertility. A search was carried out for literary sources published in the NSBI database PubMed, Medline, and others with a search depth of up to 20 years. 135 sources on this topic were studied, of which 54 were included in the analysis. The review presents data obtained in animal studies, in vitro and in clinical studies. Thus, the absence of vitamin D resulted in a dramatical decrease in fertility in both female and male rats and mice, due to the development of hypocalcemia. In vitro studies describe its involvement in the receptive transformation of the endometrium and in the regulation of the immune response during embryo implantation. However, clinical studies often show conflicting results. There is no unequivocal data on the effect of vitamin D levels on spermogram parameters, but a decrease in the pregnancy rate was shown when ovulation was induced in pairs, where a vitamin D deficiency was revealed in men. A meta-analysis published in 2017 showed a decrease in the pregnancy and live birth rate in women with low levels of vitamin D after the use of assisted reproductive technologies (ART). It was not possible to establish whether this decrease depends on oocyte quality or endometrium. There is an opportunity that the effect of vitamin D deficiency on fertility will not come with all forms of infertility. For example, in women with anovulation due to polycystic ovary syndrome, vitamin D deficiency is demonstrated to decrease pregnancy rate in ovulation induction cycles and in ART. Such relationship was not found in women with unexplained infertility.Thus, the role of vitamin D in the pathogenesis of infertility requires further study, as well as the possibilities of therapy in order to increase the effectiveness of infertility treatment methods and assisted reproductive technology programs.