8th February 2024

Electrolyte balance and vitamin D metabolism

As we have seen already, the kidneys can influence the levels of some electrolytes within the body. Low calcium levels stimulate PTH release from the parathyroid glands. PTH acts on the kidneys to reduce calcium and magnesium loss in the urine and increase phosphate excretion. 

PTH also stimulates the activation of vitamin D in the kidneys thanks to the production of alpha-1-hydroxylase by the proximal tubular cells. This enzyme catalyses the conversion of 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol (calcitriol). Calcitriol then stimulates absorption of calcium, phosphate and magnesium from the gastrointestinal tract. In CKD, the production of alpha-1-hydroxylase drops.