A multiple linear regression analysis was performed to evaluate the effect of BMI, age, sex, nicotine abuse, the season of sampling, history of medication (glucocorticoids, L-thyroxine, proton-pump inhibitors, and aromatase inhibitors), and secondary diagnoses (diabetes, rheumatic disease, COPD, and carcinoma) on their potential influence as predictive variables for preoperative vitamin D serum levels. Here, CYP19A1 is linked to diabetes mellitus.