Serum 1, 25 dihydroxy vitamin D (1, 25(OH)2D3), 25 hydroxy vitamin D (25(OH)D), and parathormone levels in diabetic retinopathy. - Aksoy,H.; Akcay,F.; Kurtul,N.; Baykal,O.; Avci,B. (Clin Biochem, 2000)