What action does PTH have on renal function?

Parathyroid hormone (PTH) plays a crucial role in regulating calcium and phosphate metabolism in the body, particularly in the kidneys. One of the main effects of PTH on renal function is to decrease the excretion of phosphate. PTH promotes the reabsorption of calcium in the renal tubules while simultaneously inhibiting the reabsorption of phosphate, leading to an increase in phosphate excretion; however, the action relevant to the selected answer refers to how PTH affects overall phosphate levels in the body.

In terms of renal handling, PTH acts to decrease the renal tubular reabsorption of phosphate, which is echoed in its function of mobilizing calcium from bones and increasing intestinal absorption of calcium (aided by vitamin D). By promoting a lower phosphate level in the serum, PTH helps to maintain a balance between calcium and phosphate, crucial for various physiological processes.

While PTH also stimulates the production of active vitamin D (calcitriol) in the kidneys, which aids in increasing calcium absorption and indirectly affects phosphate, the direct action that decreases phosphate excretion through renal processes solidifies the understanding of how PTH functions in maintaining mineral homeostasis.