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NBME 21 Answers

nbme21/Block 4/Question#31 (29.7 difficulty score)
A 48-year-old woman comes to the physician ...
Paracrine stimulation of osteoclasts by osteoblasts🔍
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submitted by tinydoc(190),
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pg32  Picked D despite understanding the above ^^ because IL-1 is also known as osteoclast acitivating factor... +6  
plzhelp123  ^ I did the same, but it appears that IL-1 activates osteoclasts in multiple myeloma. Which makes sense as that is a neoplasm of immune cells which can produce interleukins. +  
caitlyncloy  can anyone explain why this the answer is "PARACRINE" stimulation?? I rule out the correct answer because i was picturing RANK and RANK L binding, which is not paracrine?! +  
caitlyncloy  oh.. it seem RANK L is secreted to activate the clasts.. i was picturing it as RANKL was on the surface of the blast. reference: https://www.youtube.com/watch?v=hOIBRJeetAs +  

Primary hyperparathyroidism: overproduction of PTH by parathyroid chief cells Effect of PTH on bone → increased bone resorption → ↑ release of calcium phosphate → ↑ calcium levels

Induces RANKL expression in osteoblasts → binding of RANKL to RANK on osteoclasts → activation of osteoclasts

Induces IL-1 expression in osteoblasts → activation of osteoclasts

Not sure why D is wrong

+1/- alexv0815(-1),