NBME 20 Teratogenic effects in the embryo (NBME Answers)

Retired NBME 20 Answers

nbme20/Block 3/Question#39 (reveal difficulty score)
A 19-year-old woman has severe refractory ...
Teratogenic effects in the embryo 🔍 / 📺 / 🌳 / 📖
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+9 upvote downvote
submitted by ∗garima(21)

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I think the question asks 'if it binds to RXR, what happens?'

The retinoid X receptor (RXR1) is an intriguing and essential member of the steroid/thyroid hormone superfamily of nuclear receptors (NRs) that predominately function as transcription factors with roles in development, cell differentiation, metabolism, and cell death

which means its related with development etc

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bend_nbme_over Definitely a poorly worded question for sure +

+7 upvote downvote
submitted by ∗hayayah(1212)

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Isotretinoin is used to treat severe cystic acne. It is a teratogen. Can cause multiple severe birth defects. Contraception is mandatory. RXR is a retinoid X receptor.

IsoTERATinoin

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+7 upvote downvote
submitted by ∗mbourne(118)

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This is a mish-mash of information I can find on this subject. Can't find good info on this anywhere. I think this question sucks

"Isotretinoin has a low affinity for retinoic acid receptors (RAR) and retinoid X receptors (RXR), but may be converted intracellularly to metabolites that act as agonists of RAR and RXR nuclear receptors.

In the nucleus of a cell, retinoic acid acts as a ligand, which is a molecule that binds to a site on a specific protein, to activate two families of transcriptional factors. These two families are the retinoic acid receptors (RAR) and retinoid X receptors (RXR), which bind to genes that respond to retinoic acid. There are three forms of RARs and three forms of RXR.

Studies with in vitro rat embryos have shown that retinoids act directly on the embryo, causing those embryo to develop abnormally."

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euchromatin69 u world 1568 flow chart +5

athenathefirst Anyone can justify why it's not A? decreased P acnes also depends on the drug binding to the RXR receptor. So how can A cannot be correct also? Ughhh so stressed with this stupid NBME wording. +2

coco Retinoids bind to the RXR receptor and inhibit follicular epidermal keratinization(normalize epidermal differentiation), thereby loosening the keratin plugs of comedones and facilitating their expulsion. They also reduce the size of sebaceous glands and inhibit sebum production.But retinoid would not direcly reduce P.acne.Antibiotics reduce P.acne +

+5 upvote downvote
submitted by ∗whossayin(35)

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the question was very poorly worded in my opinion, anybody else agree?

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niboonsh yea it was a dumbass question, whoever is writing these questions is undoubtedly a crazy genius but homeboy (or homegirl...homeperson?) needs a few grammar lessons. +4

yex I agree. We know that it is a teratogen, but how does that question directs you to think about teratogenic effects instead of something physiologic? +6

dr_jan_itor The questions in the NBMEs by default are reject questions. So highly selective to be awful questsions. I am recieving regular heads up that the stems on the real thing lately are like 10-12 lines long. So these questions are not anywhere near like the test. NBME has f'd us good for this particular round of practice forms. +

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