A 4X decrease in 1,25-(OH)2-VDR density has been reported in the PTGs of experimentally uremic dogs.143 The VDR in the PTG is upregulated by calcitriol; so, it is likely that low circulating calcitriol during CKD accounts for most of the downregulation of the VDR in this tissue. Here, VDR is linked to chronic kidney disease.