The Relationship between Vitamin D Metabolites and Androgens in Women with Polycystic Ovary Syndrome

Causal association between low vitamin D and polycystic ovary syndrome: a bidirectional mendelian randomization study

BACKGROUND

Recent studies have revealed the correlation between serum vitamin D (VD) level and polycystic ovary syndrome (PCOS), but the causality and specific mechanisms remain uncertain.

OBJECTIVE

We aimed to investigate the cause-effect relationship between serum VD and PCOS, and the role of testosterone in the related pathological mechanisms.

METHODS

We assessed the causality between serum VD and PCOS by using genome-wide association studies (GWAS) data in a bidirectional two-sample Mendelian randomization (TS-MR) analysis. Subsequently, a MR mediation analysis was conducted to examine the mediating action of testosterone in the causality between serum VD and PCOS. Ultimately, we integrated GWAS data with cis-expression quantitative loci (cis-eQTLs) data for gene annotation, and used the potentially related genes for functional enrichment analysis to assess the involvement of testosterone and the potential mechanisms.

RESULTS

TS-MR analysis showed that individuals with lower level of serum VD were more likely to develop PCOS (OR = 0.750, 95% CI: 0.587-0.959, P = 0.022). MR mediation analysis uncovered indirect causal effect of serum VD level on the risk of PCOS via testosterone (OR = 0.983, 95% CI: 0.968-0.998, P = 0.025). Functional enrichment analysis showed that several pathways may be involved in the VD-testosterone-PCOS axis, such as steroid hormone biosynthesis and autophagy process.

CONCLUSION

Our findings suggest that genetically predicted lower serum VD level may cause a higher risk of developing PCOS, which may be mediated by increased testosterone production.

Effect of metformin versus metformin plus liraglutide on gonadal and metabolic profiles in overweight patients with polycystic ovary syndrome

OBJECTIVE

To observe the effect of metformin (MET) monotherapy versus MET plus liraglutide (LIRA) on gonadal and metabolic profiles in overweight patients with polycystic ovary syndrome (PCOS).

METHODS

Sixty overweight patients with PCOS were recruited from January 2021 to January 2022 in Shengjing Hospital of China Medical University and were randomly assigned to the MET or combination (COM) group to receive 12 weeks of MET monotherapy or MET plus LIRA therapy. Anthropometric measurements, menstrual cycle changes, gonadal profiles, and oral glucose tolerance tests (OGTT) were conducted at baseline and after the 12-week treatment.

RESULTS

Fifty-two subjects completed the trial while eight were lost during the follow-up. Both MET and COM improved menstrual cycles, anthropometric parameters, and glucose metabolism after the 12-week treatment; however, there was no statistical difference between the two groups. MET plus LIRA therapy improved hyperandrogenemia, including TT (total testosterone), SHBG (sex hormone binding globulin) and FAI (free androgen index), whereas MET monotherapy only improved SHBG and FAI when compared with baseline. Furthermore, both MET monotherapy and MET plus LIRA therapy improved E2 (estradiol) while only MET plus LIRA therapy improved LH (luteinizing hormone), FSH (follicle stimulating hormone) and Prog (progesterone) more effectively than baseline. Additionally, MET plus LIRA therapy may improve TT, SHBG, FAI, LH and Prog more effectively than MET monotherapy; however, there were no significant differences on E2, FSH and LH/FSH between the two groups.

CONCLUSIONS

In overweight patients with PCOS, both MET monotherapy and MET plus LIRA therapy improved glucose metabolism and relieved insulin resistance (IR). Additionally, MET plus LIRA therapy was more effective than MET monotherapy in improving reproductive abnormalities and hyperandrogenemia, potentially by modulating the hypothalamic-pituitary-ovarian axis.

Low Serum 25-Hydroxyvitamin D Levels Are Associated With Hyperandrogenemia in Polycystic Ovary Syndrome: A Cross-Sectional Study

BACKGROUND

Increasing evidence suggests a link between vitamin D and polycystic ovary syndrome (PCOS). However, whether vitamin D is related to hyperandrogenemia in PCOS is still inconclusive. The aim of our study is to elucidate the relationship between vitamin D and hyperandrogenemia in women with PCOS in China.

METHODS

This is a cross-sectional study including 625 Chinese women with PCOS and 217 controls from January 2016 to June 2020. The anthropometric and biochemical parameters related to 25(OH)D, sex steroids, glucose and lipid profiles were measured.

RESULTS

Serum 25(OH)D levels were lower in women with PCOS than controls (33.99 ± 15.05 vs 36.58 ± 16.49 nmol/L, P = 0.034), especially lower in hyperandrogenic women with PCOS (32.79 ± 14.24 vs 36.21 ± 16.27 nmol/L, P = 0.007). Higher 25(OH)D levels were independently associated with lower risks of hyperandrogenemia after adjusting demographic, metabolic and hormonal confounders (OR = 0.982, 95% CI: 0.969 - 0.995, P = 0.006). Consistent results were observed in subgroup analyses. Among PCOS women with vitamin D deficiency, females with age ≥ 26 years had lower risks of hyperandrogenemia (OR = 0.611, 95% CI = 0.389 - 0.958, P = 0.032), while overweight patients had higher risks of hyperandrogenemia (OR = 2.202, 95% CI = 1.130 - 4.293, P = 0.020) after adjusting multiple confounders.

CONCLUSIONS

Our study reported lower vitamin D levels in Chinese women with PCOS, especially in those with hyperandrogenemia. An independent negative correlation between 25(OH)D and hyperandrogenemia was noted in PCOS. For PCOS women with vitamin D deficiency, females that have higher BMI with age < 26 years may be prioritized for hyperandrogenemia assessment.

Mechanisms Involved in the Relationship between Vitamin D and Insulin Resistance: Impact on Clinical Practice

Recent evidence has revealed anti-inflammatory properties of vitamin D as well as extra-skeletal activity. In this context, vitamin D seems to be involved in infections, autoimmune diseases, cardiometabolic diseases, and cancer development. In recent years, the relationship between vitamin D and insulin resistance has been a topic of growing interest. Low 25-hydroxyvitamin D (25(OH)D) levels appear to be associated with most of the insulin resistance disorders described to date. In fact, vitamin D deficiency may be one of the factors accelerating the development of insulin resistance. Vitamin D deficiency is a common problem in the population and may be associated with the pathogenesis of diseases related to insulin resistance, such as obesity, diabetes, metabolic syndrome (MS) and polycystic ovary syndrome (PCOS). An important question is the identification of 25(OH)D levels capable of generating an effect on insulin resistance, glucose metabolism and to decrease the risk of developing insulin resistance related disorders. The benefits of 25(OH)D supplementation/repletion on bone health are well known, and although there is a biological plausibility linking the status of vitamin D and insulin resistance supported by basic and clinical research findings, well-designed randomized clinical trials as well as basic research are necessary to know the molecular pathways involved in this association.

Different threshold levels of circulating total and free 25-hydroxyvitamin D for the diagnosis of vitamin D deficiency in obese adolescents

The total serum 25-hydroxyvitamin D [25(OH)D_T] level is lower in obese individuals than in their nonobese peers, despite similar bone turnover markers and bone mineral density. This study aimed to investigate whether the threshold level of 25(OH)D for the diagnosis of vitamin D deficiency (VDD) in obese adolescents was lower than that in controls and to compare 25(OH)D_T, free [25(OH)D_F] and bioavailable [25(OH)D_B] vitamin D with VDBP levels in obese individuals and their controls. A total of 173 adolescents (90 obese individuals and 83 controls) aged 12-18 years were included in the study. The metabolic and anthropometric parameters of the participants were recorded, the 25(OH)D_T, 25(OH)D_F, and VDBP levels were measured, and the 25(OH)D_B levels were calculated. The cutoff values for VDD were estimated according to the level of 25(OH)D below which parathyroid hormone begins to rise. The obese subjects had lower 25(OH)D_T (12.1 ± 5.8 vs. 16.4 ± 9.3 ng/mL, p < 0.001), 25(OH)D_F (12.6 ± 4.2 vs. 16.7 ± 7.6 pg/mL, p < 0.001), 25(OH)D_B [4.8 (2.3) vs. 6.1 (5.2) ng/mL, p = 0.012], and VDBP [112.2 (51.3) vs. 121.9 (95.5) μg/mL, p < 0.001] levels than the controls. The cutoff values for 25(OH)D_T and 25(OH)D_F levels for VDD were lower in the obese group than in the control group (9.4 vs. 14.1 ng/mL; 12.2 vs. 16.8 pg/mL, respectively).Conclusion: The vitamin D cutoff values for the diagnosis of VDD were different in the obese and control groups. Using the same cutoff value for VDD may cause overtreatment in obese adolescents. What is Known: • Vitamin D deficiency is more prevalent in obese children than nonobese controls, despite the same bone turnover markers and bone mineral density • The cutoff value of vitamin D level for the diagnosis of VDD is based on the PTH elevation What is New: • In obese adolescents, total and free vitamin D cutoff value for the diagnosis of VDD was lower than nonobese peers • Using the same cutoff value for vitamin D deficiency in both obese and nonobese adolescents may cause overtreatment.

Vitamin D deficiency effects on cardiovascular parameters in women with polycystic ovary syndrome: A retrospective, cross-sectional study

PURPOSE

Polycystic ovary syndrome (PCOS) is associated with vitamin D deficiency (25-hydroxyvitamin D (25(OH)D), and both are associated with increased cardiovascular risk; therefore, the combination of PCOS and moderate vitamin D deficiency may exacerbate the cardiovascular and metabolic characteristics in women with PCOS. This study sought to address this question.

METHODS

In this retrospective, cross-sectional study, demographic and metabolic data from women aged 18-40 years from the Qatar Biobank (QBB) (78 diagnosed with PCOS, 641 controls) was analyzed.

RESULTS

Moderate vitamin D deficiency was seen in both normal and PCOS cohorts irrespective of body mass index (BMI) stratification into normal, overweight and obese. Significant differences in free androgen index (FAI) and high density lipoproteins (HDL) (p < 0.05) were seen in PCOS irrespective of BMI, though insulin resistance and increased C-reactive protein (CRP) (p < 0.05) were seen only in obese PCOS subjects; however, there was no correlation (Pearson coefficient) of any these parameters with vitamin D for women with or without PCOS, nor when vitamin D deficiency was compared to vitamin D insufficiency (above and below 20 ng/mL, respectively) between the normal and PCOS groups.

CONCLUSION

Moderate vitamin D deficiency did not associate with nor exacerbate insulin resistance, androgen levels, inflammation or cardiovascular risk indices in women with PCOS, suggesting that a prospective study on vitamin D deficiency to confirm non-causality is required.

A Narrative Review of Current Understanding of the Pathophysiology of Polycystic Ovary Syndrome: Focus on Plausible Relevance of Vitamin D

Polycystic ovarian syndrome (PCOS) is the most prevalent endocrinopathy of reproductive years. Salient features in presentation of patients PCOS include menstrual dysfunction, hyperandrogenism and/or polycystic appearance of ovaries on ultrasound. While the diagnosis of PCOS depends on presence of specified criteria, misdiagnoses are common. Despite years of extensive research, the exact aetiology of PCOS remains largely unknown. In the past decade, apart from insulin resistance and hyperandrogenemia, anti-mullerian hormone (AMH), an important marker of ovarian reserve, and vascular endothelial growth factor (VEGF), a crucial factor in angiogenesis, have been examined as plausible players of causative relevance for PCOS. Vitamin D, a sex-steroid hormone that is universally known for its relevance for skeletal health, has received increasing attention due to growing evidence supporting its pivotal in reproductive physiology and in PCOS. In this review we summarize our current understanding of the mechanisms relevant to the pathophysiology of PCOS and examine the role of vitamin D signalling in this context.

Relationship Between Vitamin D and Hormones Important for Human Fertility in Reproductive-Aged Women

Vitamin D deficiency is very common in women of reproductive age. Studies in animals suggests a link between vitamin D and reproductive hormone biosynthesis. A systematic analysis of the correlation of reproductive hormones in reproductive-aged women with both total and free vitamin D was, however, not done so far. This cross-sectional study was performed in 351 healthy reproductive age Caucasian women (median age, 28.0 years; interquartile ranges, 24.7-31.0 years). We measured serum levels of both total and free 25(OH)D, endocrinological, hematological and biochemical parameters. Spearman's rank correlations were performed to assess the correlation between 25(OH)D metabolites and selected parameters. Total vitamin D and free vitamin D measurements correlated well (rho=0.912, p < 0.0001). Both total 25(OH)D and free 25(OH)D showed significant negative correlation with FAI (rho=-0.229, p<0.0001 and rho=-0.195, p<0.0001 for total and free 25(OH)D, respectively); LH (rho=-0.177, p=0.001 and rho=-0.114, p=0.04 for total and free 25(OH)D, respectively), testosterone (rho=-0.174, p=0.001 and rho=-0.190, p<0.0001 for total and free 25(OH)D, respectively) and AMH (rho=-0.130, p=0.015 and rho=-0.107, p=0.047 for total and free 25(OH)D, respectively). Our study showed comparable correlations of both total and free 25(OH)D with endocrinological parameters, i.e. inverse correlations with free androgen index, luteinizing hormone, testosterone, LH/FSH ratio, androstenedione and anti-Müllerian hormone, and also with hematological and biochemical parameters, i.e. inverse correlations with erythrocytes, hsCRP and leukocytes count, and positive correlation with transferrin saturation, mean corpuscular hemoglobin and mean corpuscular volume in healthy reproductive age women.