Polycystic ovary syndrome and 25-hydroxyvitamin D: A bidirectional two-sample Mendelian randomization study

Area of Science:

• Endocrinology
• Genetics
• Nutritional Science

Background:

• Vitamin D deficiency (serum 25-hydroxyvitamin D < 50 nmol/L) is frequently observed in women with polycystic ovary syndrome (PCOS).
• The causal relationship between PCOS and vitamin D deficiency remains unclear.
• Observational studies suggest a link, but the directionality and causality require investigation.

Purpose of the Study:

• To investigate the potential causal association between polycystic ovary syndrome (PCOS) and vitamin D levels.
• To explore the bidirectional relationship between PCOS and 25-hydroxyvitamin D (25OHD) using Mendelian randomization.

Main Methods:

• A bidirectional two-sample Mendelian randomization (MR) study was conducted.
• Genome-wide association studies (GWAS) summary statistics for PCOS and 25OHD were utilized.
• Univariate and multivariable MR analyses were performed, adjusting for obesity and insulin resistance.

Main Results:

• Univariate MR indicated a negative association between genetically determined PCOS and 25OHD levels.
• This causal effect of PCOS on 25OHD disappeared in multivariable MR when adjusting for obesity and insulin resistance.
• No significant causal effect of vitamin D deficiency on the risk of PCOS was found.

Conclusions:

• The apparent causal effect of PCOS on vitamin D deficiency may be mediated by obesity and insulin resistance.
• There is no substantial evidence for a causal effect of vitamin D deficiency on the risk of developing PCOS.
• Further research, including observational studies and clinical trials, is warranted.