Individuals with vitamin D deficiency (25-hydroxyvitamin D levels below 50 nmol/L) exhibited notably reduced levels of total testosterone and sex hormone-binding globulin (SHBG) in comparison to those with vitamin D insufficiency and optimal levels (statistically significant with p <0.05). However, these differences became statistically nonsignificant after adjusting for body mass index (BMI) (p > 0.05). The gene discussed is SHBG; the disease is vitamin D deficiency.