Another limitation was the lack of information on serum estradiol and 1,25-dihydroxyvitamin D concentration, the prevalence of osteoporosis, genetic analysis of single nucleotide polymorphisms of genes encoding vitamin D-binding protein and 25-hydroxylase, and on other potential confounders such as the use of supplements, clothing style and sunscreen use. The gene discussed is GC; the disease is osteoporosis.