Renal failure, parathyroid hormone and extrarenal disposal of potassium.

Parathyroid hormone (PTH) impairs extrarenal disposal of potassium in both acute and chronic renal failure. This effect is due to the property of the hormone that facilitates entry of calcium into cells since a rise in cytosolic calcium affects cellular permeability to potassium. On the other hand, calcium channel blockers enhance translocation of potassium from extracellular space into cells and this effect of these agents is related to their ability to prevent calcium entry into cells. Since patients with chronic renal failure have elevated blood levels of PTH, the effect of the hormone on extrarenal disposal of potassium should have important clinical implications. Chronic renal failure patients with higher blood levels of PTH may be at a greater risk of hyperkalemia when exposed to a potassium load than those with lower levels of PTH. Thus, in developing dietary regimens for potassium intake to patients with chronic renal failure, their blood levels of PTH should be taken into consideration in such dietary planning.