Is serum vitamin D level a risk factor for idiopathic male fertility?

Background: Idiopathic male infertility is a health problem that is increasingly common worldwide. Aetiology of idiopathic male infertility is still controversial. In this cross-sectional retrospective study, we aimed to investigate the relationship between serum vitamin D level and sperm quality in patients with idiopathic male infertility. Methods: Between June 2018 and June 2020, 297 patients including 147 men with idiopathic infertility (as a study group) and 150 fertile men (as a control group) were retrospectively enrolled into the study. Blood samples were collected, and these samples included serum sex steroids, serum vitamin D levels, glucose tests, lipid profiles, liver function tests and kidney function tests. At least two sperm analyses, scrotal doppler ultrasonography and karyotype analysis were performed on each of the patients. Demographic, laboratory and radiological features were also recorded. The Mann Whitney-U test was used to compare groups and quantitative independent data. The Chi-square test was used for qualitative independent data. Spearman's correlation analysis was applied for correlation. Significant results were investigated and analysed further using the logistic regression test. Results: The mean age of the patients was 31.98 +/- 6.97 years. The mean serum vitamin D level of the patients was 23.16 +/- 10.40 ng/dL and the mean infertility duration of patients with idiopathic infertility was 29.88 +/- 28.86 months. We observed statistical significance in terms of serum vitamin D levels, impaired total sperm motility, progressive sperm motility and sperm morphology in idiopathic infertile men when compared to fertile men. There were no statistically significant between idiopathic infertile men and fertile men in terms of serum testosterone levels. Conclusions: We observed a positive correlation between serum vitamin D levels and impaired sperm parameters, specifically in terms of sperm morphology, total sperm motility and progressive sperm motility. Vitamin D supplementation may be a beneficial contribution to achieving high paternity rates in men with idiopathic male infertility.