bone mineral homeostasis Flashcards
what are the control sites for plasma Calcium and PO4
gut, blood, bone. kidney
which bone cell is responsible for deposition of bone
osteoblasts
which bone cell is responsible for resorption of bone
osteoclasts
how are osteoclasts activated? draw a flowchart.
hormones activate osteoblasts
osteoblasts secrete RANK ligand
RANK ligand activates osteoclasts
Parathyroid hormone promotes or inhibits
______ bone resorption
_______ Ca absorption in the kidney
_______ PO4 excretion
promotes
promotes
promotes
What is the net affect of PTH on Calcium and PO4`
increase calcium
decrease (sort of) PO4
what is PTH 1-34
synthetic parathyroid hormone
what is teriperatide ?
what is it used for?
PTH 1-34, synthetic hormone
osteoperosis
how does PTH affect the kidney ASIDE from affecting the Ca and PO4 concentrations?
stimulation of vitamin D processing
T or F
PTH directly promotes bone resorption.
explain
FALSE
not directly, INDIRECTLY.
PTH –> osteoblast —–> RANKL ——> osteoctye ——> resorption
where is vitamin D metabolized
liver then kidney
what is vitamin D metabolized into? (2)
calcitriol (active form)
secalciferol
Vitamin D3: (fill in the blanks)
________ Ca excretion
_______ PO4 excretion
________ Ca concentration through bone resorption
_________ PO4 concentration through bone resorption
decrease
decrease
increase
increase
how does vitamin D affect Ca and PO4 in the gut?
promotes uptake
what are Ca levels sense by?
Ca receptors in the parathyroid
PTH exerts effects on PTH receptors in the _______ and _______
kidney and osteoblasts
PTH stimulation of vitamin D metabolism leads to vitamin D effects in _____, _____ and _____
gut, kidney and bone
what is the active form of Vitamin D
1,25 form
what are the effects of FGF23?
inhibits phopshate uptake
inhibits D3 metabolism
inhibits PTH production
what are the effects of calcitonin?
INHIBITS bone resoprtion
inhibits calcium and phosphate reabsorption in kidney
where was calcitonin discovered, and by whom?
UBC, D.H Copp
what effects do glucocorticoids have on bones? why?
osteoporosis
because it blocks calcium uptake in gut and promotes excretion in the kidney
how do estrogens affect bones?
PREVENT bone loss in postmenopausal women
direct effects in bone, prevents PTH stimulated resorption
what is hypocalcemia?
too little calcium
how can hypocalcemia be treated?
calcium (oral, iv or im)
or an active vitamin D3 metabolite
what are the negative effects of hypocalcemia?
hyperexcitability in cells
seizures, muscle tetany, spasms
what is the long-term danger of hypocalcemia:?
what does it cause?
HYPERPARATHYROIDISM
weakening of bones
what is the long term underlying defect causing hypocalcemia?
hypoparathyroidism
vitamin D deficiency
how can hypoparathyroidism be treated?
vitamin D OR calcium supplements
how can vitamin D deficiency be treated
ingestion of active vitamin D3 metabolites (like calcitrol)
sunshine
how does hypercalcemia affect cellular excitability
loss of cellular excitability
lethargy is caused by _____
hyper or hypocalcemia
hypercalcemia
what is the long-term cause of hypercalcemia usually?
primary hyperparathyroidism
what are calciimimetics? what do they treat?
synthetic calcium, mimic calcium affect on receptors to increase excitability
hypercalcemia
name 3 modes of therapy for hypercalcemia?
- resection of PT gland
- protect the bone
- calcimimetics
which demographic is most affected by osteoperosis?
aging females
what is teriparatide?
what does it treat?
recombinant fully active PTH fragment
osteoporosis
why is teriparatide strange?
how does it work despite this feature?
it is meant to fix osteoporosis, but it is a PTH fragment.
must be timed correctly to tip balance to osteoblast activity rather than RANKL activation of osteoclasts
what are biphosphates used for clinically?
how do they work?
what is the side affect that they are speculated to have?
osteoporosis
inhibition of osteoclast resorption of bone
inhibit glucocorticoid effects
what is alendronate?
biphosphate
what structure do all biphosphates have?
2 phosphonate groups
what is osteoprotegerin ? how does it work?
binds to RANKL to inhibit RANK
PTH is a _____
peptide or steroid hormone
peptide