Flashcards in osteoporosis Deck (85)
Osteoporosis: Occurs when rate of bone _______ exceeds rate of bone _______
what is the normal bone resorption process?
osteoclasts activation stimulated by RANKL
what is the activation of bone resorption in the pathologic process?
osteoclasts activation stimulated by PTH
what is the process of bone formation? what are the 4 natural substances that promote this?
Inhibition of osteoclast, stimulation of osteoblasts
IL-10 inhibit osteoclast
what two main groups of natural substances regulate bone metabolism? what does is group include?
PTH, calcitonin, estrogen, androgens
Vitamin D, glucocorticoids
what do osteocytes do?
-formed after osteoblast activity
-release chemicals that say we need more osteroblast or clast activity (regulators)
what is OPG? (where does it come from and what does it do?)
released by osteocyte, it inhibits bone resorption by binding RANKL (holding it hostage so it cant activate osteoclasts)
what does RANKL do?
binds to RANK on osteoclast - activates the osteoclast
how does PTH exposure differ with release low intermittent vs high chronic?
low intermittent- bone formation (anabolic axn)
high chronic- bone resorption (breakdown) (catabolic axn)
how does PTH increase bone turnover?
PTH stimulate osteoblast to secrete IL-1, IL-6 and RANKL to activate osteoclast activity
RANKL binds to RANK proteins triggering the osteoclasts
Result is bone turnover and remodeling
PTH regulates what two substances? using what 3 organs?
Regulates calcium & phosphate using bone, kidney, and intestines
what does PTH do in the kidney?
Stimulates 1- α hydroxylase to convert calcidiol to calcitriol (to give active vitamin D - allows us to absorb Ca+ from intestine)
-tell kidney to keep Ca+ (DistalT) but get rid of phosphate (ProximalT)
what does PTH do in the intestine?
Indirectly increases intestinal calcium absorption by stimulation of 1,25 dihydroxyvitamin D production
Vitamin D: Increases serum ___and contributes to bone ______
why is it so important to maintain Ca+ and phosphate balance? - (what if they get too high?)
need to maintain so they dont precipitate and accumulate in places like the lungs
what is the net effect of calcitonin?
Increase serum calcium -> calcitonin secretion -> inhibition of osteoclast -> decreased serum calcium
what is a hypocalcemic hormone that OPPOSES the effect of PTH?
estrogen's effect on osteocyte, blasts and clasts
- decrease osteocyte and osteoblasts apoptosis
-increase osteoclast apoptosis
what is estrogen good for in regards to bone health? why is this important?
Estrogen is better at preventing bone loss than building bone.
dont give post- menopausal women estrogen to increase bone density unless last resort (other agents are better)
glucocorticoid's effect on bones?
Antagonize vitamin D effect (decreasing intestinal calcium transport)
Blocks bone formation by inhibiting osteoblast activity
=overall : block bone formation
prolonged exposure to steroids can cause what effects in adults? children?
prolonged exposure to steroids can cause osteoporosis in adults and stunts skeletal development in children
what Can be useful at reversing hypercalcemia associated with lymphomas?
7 agents used to affect bone mineralization
Human parathyroid hormone related peptide analogs
Drug of choice (first line) for treatment of osteoporosis
what are the bisphosphonate drugs?
*Risedronate (Actonel, Atelvia)
Zolendronic acid (Reclast)- IV formulation (once a year infusion)
only bisphosphonate that is not first line b/c no help for hip/nonvertebral fractures
which bisphosphonate is IV formulation - (once a year infusion)
bind Ca+ - taken into bone in high concentrations
they are taken up by osteoclast (and destroy the proteins that make their fringe border so they can’t chew up the bone)
= osteoclast apoptosis = decr rate of resorption
what is important to remember about the abs. of oral bisphosphonates?
When given orally little is absorbed – less than 1%
must take on empty stomach for max absorption