VDR and Abnormal renal physiology: This can result in low serum 25-hydroxyvitamin D and calcitriol levels, in addition to vitamin D resistance due to loss of vitamin D receptors in the parathyroid gland and impaired binding of vitamin D to the vitamin D receptors.26 In the current study, 13 patients (23%) had documented renal dysfunction (chronic kidney disease or end-stage renal disease on hemodialysis).