Calcitriol has long been reported to provide benefits to the human uremic patient by lowering PTH concentration;130,158 this has also been reported for dogs and cats.145,159 Oral calcitriol has been shown to increase survival in human patients with CKD including those treated prior to dialysis,150,151 and in one placebo-controlled study in dogs with CKD as described earlier.b Various studies that show increased survival can be attributed to the salutary effects of extrarenal tissue VDRA, intrarenal VDRA, and benefits of lowered PTH synthesis and secretion following VDRA in the PTG. This evidence concerns the gene PTH and chronic kidney disease.