Objective: The aim of the study was to investigate the relationship between serum level of vitamin D, semen analysis parameters and sperm DNA damage in men with unexplained subfertility.
Patients and methods: Fifty-eight men diagnosed with unexplained infertility and 50 age and BMI matched fertile men were included in the study. A participant whose semen parameter is normal but pregnancy is not achieved was accepted as unexplained male infertility. Blood samples were taken from all participants following three-day abstinence for measurement of vitamin D. Sperm DNA damage was assessed by Aniline Blue staining of the collected samples.
Results: Compared with the fertile men, male patients with unexplained infertility had significantly lower vit D levels (27.00 ng/mL (12.63-39.30) vs. 23.66 ng/mL (7.50-55.00), p<0.004). While the number of patients with vitamin D levels lower than 20 ng/mL was 26 (44.8%) in the infertile group, it was recorded as 5 (10.0%) in the fertile group (p<0.001). DNA damage was found in 31.50% (9.0-71.0) of the infertile men and 26.00% (11.0-54.0) of the fertile men. DNA damage was found to be significantly higher in the unexplained infertile group (p<0.002). In men with unexplained male infertility, serum vit D levels were positively correlated with total sperm count (r = 0.527, p<0.001), total motility (r = 0.527, p<0.001) and sperm morphology (r = 0.416, p = 0.001). There was a negative and significant correlation between vit D levels and sperm DNA damage (r = -0.605, p<0.001). In the logistic regression analysis, serum vit D > 20 ng/mL led to an improvement in fertility outcome.
Conclusions: Men with unexplained infertility exhibit decreased serum vit D levels and increased sperm DNA damage.