When calcium is low, PTH increases and leads to what effect on bone and renal calcium handling?

When calcium is low, PTH increases and leads to what effect on bone and renal calcium handling?

• A. Increased intestinal absorption of calcium
• B. Decreased bone deposition
• C. Increased absorption to bone; enhances bone deposition and renal excretion of calcium
• D. Decreased renal excretion of calcium

Answer: (C)

Low calcium triggers parathyroid hormone release. PTH acts to raise serum calcium by two main routes: it stimulates bone resorption, so calcium is released from bone into the blood; and it increases calcium reabsorption in the distal tubule of the kidney, which decreases urinary calcium loss. It also promotes production of active vitamin D, boosting intestinal calcium absorption. So the net effect on bone and kidneys is more calcium coming from bone and less calcium being excreted by the kidneys (with a concurrent boost in intestinal absorption).

Low calcium triggers parathyroid hormone release. PTH acts to raise serum calcium by two main routes: it stimulates bone resorption, so calcium is released from bone into the blood; and it increases calcium reabsorption in the distal tubule of the kidney, which decreases urinary calcium loss. It also promotes production of active vitamin D, boosting intestinal calcium absorption. So the net effect on bone and kidneys is more calcium coming from bone and less calcium being excreted by the kidneys (with a concurrent boost in intestinal absorption).