Calcium and Phosphorus

Question 1

what 3 hormones are responsible for regulating serum calcium and phosphorus

Answer 1

1. Parathyroid hormone
2. Vitamin D
3. Calcitonin

Question 2

describe the pathway for active vitamin D (calcitriol) formation

Answer 2

dietary cholecalciferol -> absorbed into intestines -> liver converts cholecalciferol to calcidiol -> the kidneys convert calcidiol to calcitriol

Question 3

calcitriol effect on GI tract

Answer 3

increases Ca and P absorption

Question 4

calcitriol effect on bone

Answer 4

increases bone resorption

Question 5

calcitriol effect on kidney

Answer 5

increases Ca and P reabsorption

Question 6

calcitriol effect on serum Ca and P

Answer 6

increases both

Question 7

PTH effect on bone

Answer 7

increases bone resorption

Question 8

PTH effect on kidneys

Answer 8

increases Ca reabsorption and increases P excretion

Question 9

PTH effect on intestines

Answer 9

no direct effect

Question 10

PTH effect on serum Ca and P

Answer 10

increase Ca, decrease P

Question 11

calcitriol formation is highly dependent on levels of what?

Answer 11

PTH, calcitriol and iCa

Question 12

explain the regulation of parathyroid secretion

Answer 12

PTH is synthesized and secreted by chief cells of the parathyroid gland in response to hypocalcemia. Secretion is regulated by serum iCa and increased calcitriol

Question 13

what is the principal action of PTH

Answer 13

to increase iCa through increased resorption in the kidneys, increased osteoclastic bone resorption and increased production of calcitriol