The Association Between Vitamin D and Polycystic Ovary Syndrome (PCOS) in Women: A Systematic Review.

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• Vitamin D deficiency is common in women with polycystic ovary syndrome (PCOS).

• Vitamin D supplementation may modestly improve insulin sensitivity in women with PCOS, but findings are inconsistent.

• Women with vitamin D deficiency may benefit more from supplementation, suggesting a role for assessment in those at risk.

• Vitamin D supplementation may form part of a comprehensive care plan for women with PCOS, but is not a stand alone treatment.

Introduction -

Polycystic ovary syndrome (PCOS) is characterised by abnormal androgen production, ovarian function, and insulin resistance. These can contribute to anovulation and hyperandrogenism.  Reproductive tissue has been shown to express vitamin D receptors and vitamin D deficiency has been shown to be prevalent in women with PCOS. This systematic review aimed to evaluate observational and interventional studies on the association between vitamin D and PCOS, focusing on prevalence, metabolism, and reproduction

Methods -

• This review followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines and examined observational studies and randomised control trials (RCTs) of women with diagnosed PCOS using disclosed diagnostic criteria.

• Primary outcomes were measures of insulin resistance using the homeostatic model assessment of insulin resistance (HOMA-IR), fasting insulin, quantitative insulin sensitivity (QUICKI), and 2h post-oral glucose tolerance test (OGTT), as well as reproductive measures including menstrual regularity, ovulation rate, and clinical pregnancy.

• Secondary outcomes included lipid parameters, blood pressure, inflammatory markers, and hormonal markers.

Results -

• 11 studies including 1063 women with PCOS were included in the analysis, nine RCTs and two observational studies.

• Two observational studies looked at vitamin D deficiency in PCOS, and it was concluded that vitamin D deficiency in PCOS is positively associated with obesity and insulin resistance. These studies also showed an inverse relationship between 25(OH)D and insulin resistance, body mass index, and leptin but no relationship with testosterone levels.

• Nine RCTs, ranging in length from 8-24 weeks, looked at vitamin D supplementation (12,000-60,000 IU/week) on metabolic, reproductive, and endocrine outcomes. Some studies found statistically significant improvements to insulin sensitivity with Vitamin D supplementation, however this was not consistent across all studies. Positive effects were more apparent in women with vitamin D deficiency.

• Of these nine, three RCTs looked at reproductive outcomes. Benefits were seen in two of the trials with improvements to cycle length, improved ovulation rates, and improved ovarian morphology. Seven of the nine RCTs looked at metabolic outcomes with four showing improvements to fasting insulin, fasting glucose, Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), and low density lipoprotein. However, effects were not universal across the studies with some finding benefits whereas others did not.

Conclusion -

It was concluded that vitamin D deficiency is highly prevalent in women with PCOS and is associated with insulin resistance and higher adiposity, while associations with reproductive outcomes are less consistent. Vitamin D supplementation was associated with beneficial effects to insulin resistance, hormonal parameters, and ovulatory outcomes. However, varying effects were apparent across the studies with not all of the studies reporting benefits.

• Vitamin D deficiency is prevalent in individuals with PCOS.

• Vitamin D supplementation  in women with PCOS may have modest and variable metabolic and endocrine effects and should be considered when vitamin D deficiency is present.

• However,routine vitamin D screening is not recommended solely based on a PCOS diagnosis. Consider other signs and symptoms before screening.

• Vitamin D supplementation may provide modest and variable endocrine benefits to women with PCOS, but is not a stand alone treatment.

• Baseline 25(OH)D levels should be reported in future studies to allow a more accurate assessment of outcomes.

• Future research focusing on clinical outcomes such as birth rates and type 2 diabetes development in relation to Vitamin D levels and supplementation, would enhance understanding.