calcium homeostasis :'(

Question 1

name for higher than normal calcium levels

Answer 1

hypercalcemia

Question 2

3 domains of activity

Answer 2

intake and excretion
storage
control

Question 3

intake calcium?

Answer 3

calcium absorbed across brush border of intestinal epithelial cells, immediately binds to calbindin (vitamin D dependant protein)

Question 4

what is calcitriol

Answer 4

active form of vitamin D, regulates calcium intake in intestines

Question 5

what does calcium intake in the intestines depend on?

Answer 5

adequate vitamin D

Question 6

calcium excretion?

Answer 6

via bile

Question 7

what increases renal excretion and inhibits reabsorption

Answer 7

calcitonin - more calcium lost in urine

Question 8

PTH effects on kidney?

Answer 8

reduces renal excretion (opposite of calcitonin) and processes vitamin D into calcitriol

Question 9

what gland is calcitonin from

Answer 9

thyroid gland

Question 10

how is calcium stored

Answer 10

hydroxyapatite in bones (99%)

Question 11

what does release of calcium depend on

Answer 11

normal bone activity

Question 12

what directly inhibits osteoclast activity?

Answer 12

calcitonin (from the thyroid gland)

Question 13

what indirectly stimulates osteoclast activity

Answer 13

RANK-L from osteoblasts

Question 14

what causes RANK-L to be released from osteoblasts

Answer 14

PTH

Question 15

where is parathyroid hormone excreted from

Answer 15

parathyroid gland

Question 16

when is PTH released

Answer 16

when LOW serum Ca is detected

Question 17

what does PTH act on

Answer 17

kidneys, intestines, osteoblasts

Question 18

what does the thyroid gland release in response to HIGH calcium

Answer 18

calcitonin

Question 19

what acts in opposition to PTH

Answer 19

calcitonin

Question 20

what acts in opposition to calcitonin

Answer 20

PTH

Question 21

what does calcitonin directly inhibit

Answer 21

osteoclast activity

Question 22

what two different routes is vitamin D obtained through

Answer 22

absorption of lipid soluble vitamin D in intestines
UVB generation in skin

Question 23

what happens once vitamin D is synthesised

Answer 23

undergoes two hydroxylations to reach active form
first in liver, second in kidneys

Question 24

what stimulates hydroxylation of vitamin D in kidneys

Answer 24

PTH and low calcium

Question 25

vitamin D’s three main actions

Answer 25

stimulating osteoblast to release RANK-L therefore stimulating osteoclasts to increase absorption in GI tract and kidneys

Question 26

influence of oestrogen?

Answer 26

inhibits bone resorption by inhibiting release of RANK-L from osteoblasts (leads to reduced osteoclast activity therefore less bone resorption)

Question 27

hypercalcemia response?

Answer 27

detected by thyroid which releases CALCITONIN which acts on kidneys to reduce renal uptake of calcium therefore more is lost in urine. calcitonin also inhibits osteoclast activity so less calcium is released into circulation from bone

Question 28

hypocalcaemia response?

Answer 28

parathyroid gland releases PTH. stimulates osteoblasts increasing release of RANK-L, IL/MCSF. this stimulates osteoclast differentiation and activity, and the reabsorb bone.

PTH also stimulates hydroxylation of vitamin D into active form CALCITRIOL. PTH and calcitriol increase RANK-L released from osteoblasts, increase calcium uptake in kidneys and intestine.

Question 29

different speeds of pathways for hypocalcaemia?

Answer 29

slow - bone
intermediate - intestinal uptake
fast - renal uptake