NBME 21 Paracrine stimulation of osteoclasts by osteoblasts (NBME Answers)

Retired NBME 21 Answers

nbme21/Block 4/Question#31 (reveal difficulty score)
A 48-year-old woman comes to the physician ...
Paracrine stimulation of osteoclasts by osteoblasts 🔍 / 📺 / 🌳 / 📖
tags:

+15 upvote downvote
submitted by ∗tinydoc(276)

get full access to all content ⋅ pick a username

Hyperparathyroidism causing bone lesions is via Osteoblasts increasing RANK -L expression to bind to RANK on Osteoclasts and stimulating them ---> inc Bone Resorption

get full access to all content ⋅ pick a username

pg32 Picked D despite understanding the above ^^ because IL-1 is also known as osteoclast acitivating factor... +8

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?! +1

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 +1

makingstrides If you can, I Would highly recommend looking at the sketchy pharm for this. It explains this well, in my opinion, and definitely helped me. +

jatsyuk38 Goljan I could've sworn said PTH stimulates osteoblasts to secrete IL-1 to activate osteoclasts. He also said estrogen prevents osteoporosis by inhibiting osteoblast release of IL-1...however there is also a UWorld question where it said RANK-L plays a more important role actor (over IL-1) in PTH mediated bone breakdown +1

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" Amboss

Not sure why D is wrong

+/- alexv0815(10)

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

+6/- alexv0815(10)

Must-See Comments from nbme21

nosancuck on Absorption atelectasis
assoplasty on Free T4
seagull on GM2
lnsetick on Apocrine
niboonsh on NMDA receptors are blocked by Mg2+ at the ...
drdoom on Deletion of a hydrophobic amino acid ...
hayayah on HCO3− transported in the plasma
mcl on Aortic
notadoctor on Usual interstitial pneumonitis
madojo on Genital herpes
hungrybox on Obstruction of the bile duct
jambo2222 on Lung
hungrybox on Mismatch repair
hungrybox on Hydrochlorothiazide