Calcium and Bone Flashcards
how does vit D affect calcium
stimulates calcium absorption, increases plasma conc
how does vit D affect phosphate
stimulates phosphate absorption (but less than Ca++) increases plasma conc
how does PTH affect plasma calcium
increases
how does PTH affect plasma phosphate
decreases
why does PTH decrease phosphate
to prevent Ca++ and phosphate binding and forming crystals
how does calcitonin (CT) affect plasma calcium
decrease
how does CT affect plasma phosphate
decrease
how does PTH affect kidney
controls amount of Ca++ reaborbed in distal portions of nephrone
inhibits phosphate reabsorption in kidney
How does PTH affect bone
increases bone resorption and delivery of calcium to plasma
inhibits collagen synthesis by osteoblasts
how does PTH affect vit D
it increases vit D by increasing activity of 1alpha hydroxylase.
How does Vit D affect PTH
inhibits
what are the plasma forms of calcium
free or ionized
protein bound
bound to small diffusible anions
where is more than half of the total caclium found
free or ionized
symptoms of hypocalcemia
easier to have APs, so everything is more excitable
what signs clue you into hypocalcemia that causes latent tetany
trousseau or chyvostek
symptoms of hypercalcemia
less likely to have an AP. also polyuria and kidney stones
osteoblasts
deposit bone
osteoclasts
resorption of bone
osteoprotegerin ligand (OPGL) is also called
RANK ligand
function of OPGL
activates receptors on preosteoclast cells, causes them to differetiate into multinucleated osteoclasts
osteoprotegerin (OPG) function
acts as a decoy receptor of OPGL, prevents it from biding to its receptor on preosteroclast cells
how does PTH affect bone resorption
stimulates bone resoprtion by binding to receptors on osteoblasts and causing them to release OPGL
where is vitD3 converted to active form
kidney
what is the active form of vitD called
1,25 dihydrorycholecalciferol
osteomalcia
can be due to failure of damaged kidney to produce the active form of vit D
signs of primary hyperparathyroidism
hypercalcemia, hypophosphatemia
symptoms of primary hyperparathyroidism
formation of calcium containing kidney stone
weak bones
constipation, excessive urination
when does secondary hyperparathyroidism happen
pt with disease that cause chronically low plasma calcium
symptoms of hypoparathyroidism
low calcium causes neuromuscular hyperexitability, hypocalcemic tetany
pseudohypoparathyroidism
have signs and symptoms of hhypoparathyroidism but their circulating level of PTH is normal or elevated
