PLOD1 and type 2 diabetes mellitus: Notably, deficient serum 25(OH)D was mainly observed in men with T2DM with hypogonadotropic hypotestosteronemia, which indicates a positive association between the serum 25(OH)D and total serum testosterone concentrations after adjustment for age, duration, BMI, HbA1c, FBG, FIns, HOMA-IR, HOMA-β, LH, FSH, E2, DHEA, PRL.