GPT and chronic kidney disease: Across quartiles of serum 25(OH)D, significant differences (p < 0.05) were found in smoking status, heavy alcohol drinking, vitamin D supplementation, BMI, waist circumference, cancer, sleeplessness, CKD, serum calcium, ALT, AST, Scr, albumin, triglyceride, cholesterol, total bilirubin, BUN, sUA, and HbA1c.