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NBME 21 Answers

nbme21/Block 3/Question#45 (61.1 difficulty score)
A 28-year-old man comes to the physician for ...
FructoseπŸ”
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 +12 
submitted by yo(79),
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I ustj newk atth msper dnee srctu,oef otn sreu atwh assdeei srpcose tshi is othhu.g eH aws ttreyp mroaln so 5a seucatedar se'todn rsteenp ikle atht. I stna'w rseu fi rteeh swa nay odd use fo hte htroe awn.sser eher is a lni.k leeF rfee ot ndeax.p

.c2/ea/seps:uc2o7nt..ltghbsaxt4_pqswpo2mi/ww

Fcusrteo maske pu %99 of hte geuicnrd rsuga rpetens ni m.nees ihTs uargs si odeurcdp ni eth mlinsae c.eevsils iihensDdmi vllsee fo osurctef vahe nebe hnwso ot rplleala nngerdoa dieyfcniec dan eth otoeessenrtt elv.el golFnilwo settnoreesot rhap,tye teh velle fo ucfserto iltnAoheuhr.asgesc teh ufertsco stet is ont ratp fo a enitrou seemn ,lnasyasi it si usuelf in sasce of ozoriapesam absceen( fo emspr in s.)neme nI oarieopzmsa acsonryde to eth ecenabs fo cvleessi ro fi there si na obsct,otnriu on uscoftre si te.rsenp nI taulrcseit zsiremo,apoa usftoecr si erpn.tse nehW iemsoazoarp dna lwo emnes lmuvoe tse,ixs eth tsuforce tets uodlsh saol eb eod,n no a jautotelpesac iunre maplse to ckech fro goetrrread iuectnaaljo. Tsih srcouc nwhe het aucjltaee goes oint het deldbra dnistae fo otu the trhe .aTureh erucdrope orf igmrnienedt het umtoan fo rotusfec in mesen vveonsli neiatgh enesm ni a ogsnrt dica in het senreepc fo loce.nrsiro Fouserct eigvs a edr orocl efvnfliooS( ancter)io adn mya be ared in a opmeotrh.et ehT alnmor egvaear si L3/1mdg5 orfe.tsuc

sam.l  Thank you for the explanation. I'm still confused about this answer. I was in between Zinc and fructose. Zinc deficiency also presents with anosmia (pg 71 First Aid 2019). Fructose is used for the movement. His hormones are normal. +3  
d_holles  Apparently diabetes, occlusion, and inflammation can result in ↓ fructose in sperm. Mauss et al, Fert Stert 25, 1974 https://www.fertstert.org/article/S0015-0282(16)40391-2/pdf +4  
cienfuegos  Thanks all for the info, quick note on the Zinc reply above @Sam.I: anosmia = lost sense of smell. +  
sam1  Great find yo! I believe this question was alluding to cystic fibrosis and the congenital absence of the vas deferens. Here is a link to a NEJM article about it below: https://www.nejm.org/doi/full/10.1056/NEJM196807112790203 +  
burak  zinc deficiency cause hypogonadism. there is no hypogonadism, sperms are damaged? +  
fatboyslim  @Sam1 but cystic fibrosis will show abnormal physical findings (clubbing, pulmonary crackles etc). The question says physical exam shows no abnormalities. +  
pg32  Confused as to how we can rule out zinc... From medicalnewstoday.com: "Zinc also plays a role in healthy sperm production. According to a 2018 review article in the Journal of Reproduction and Infertility, zinc deficiency may contribute to poor semen quality and infertility." +  
bekindstep1  @pg32 I am not sure of how Zinc contributes to sperm production, but the question was asking about abnormalities in the semen and fructose is present in the semen. Maybe zinc plays a role in sperm development before it is mixed in with semen and so one with zinc deficiency wouldn't have low in zinc in their semen perhaps, but it their blood. This is just a hypothesis though.... +  
brise  ^^ Yeah that's how I ruled it out. You can find fructose in the semen, but you wouldn't be able to find zinc in the semen! It might help the sperm, but it's not going to be chilling with them +  

Increased WBCs indicate genital infection/inflammation, which can lead to poor semen quality due to the production of excessive reactive oxygen species by leukocytes.

Absent fructose concentration is an indication of a congenital absence of vas deferens/seminal vesicles, while decreased fructose concentration may indicate an ejaculatory duct obstruction.

pH > 8.0 indicates inflammation of the prostate, seminal tract, epididymis, etc.; pH < 7.2 indicates seminal vesicle dysfunction or obstruction of the ejaculatory ducts.

+/- apurva(68),


 +7 
submitted by nwinkelmann(285),
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So I okdoel tnoi htis fhuterr oot cbeeaus I pretty mhcu ownk noitghn tbuao teh ekam up of .esnme Fmro eth erschare I dou,nf as sa dsttae olebw yb y,o tfcosrue is the tsmo mtntairpo tonciesuntt of nesem in etmsr ro smper cnfinout. eoBlw si rminiontfoa I ufond to edrsasd eht heotr nweras ceiho.sc

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,linalyF I tndo' thkin het l5h-aap etaecrsud ezmeyn is yacllaut in ne,mes ubt I lcodu eb ngwro. iertEh w,ya ti 'dwuotnl eb nbyolamral eletvdea ro olw if the tonseotertse eleslv aer mln.ora

bartolomoose  as per goljan, selenium is involved in glutathione peroxidase +  
chandlerbas  selenium has a role in glutathione peroxidase. excess selenium = garlic breath, hair loss, and nail changes, might see peripheral neuropathy. deficiency (pt on TPN) = dilated cardiomyopathy +  
chandlerbas  also zinc aids in sperm motility https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4773819/ thats why i chose zinc but whateverrr im over it +  



 +3 
submitted by hungrybox(977),
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ignrcocdA to hte ,MESLU mlsesi'enu ylon esu is ni nsumeeli ilusefd as a emntttaer fro a fuusng laclde asMizaesal pps Taeni( r)ocle.osrvi




 +1 
submitted by meirchod(1),

I reasoned through this one since I learned that seminal vesicles heavily use Sorbitol Dehydrogenase (and ovaries & liver I believe too), which means they probably have a particularly important need for Fructose. So abnormal fructose in semen is probably not a good sign.

P.S. I wonder if the ancients did the taste-test on this one... (seemed to work well for diabetes)




 +0 
submitted by nwinkelmann(285),
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oS I lekood niot shit rhuetrf oto eabecsu I tptrey mhcu wokn onihtng oaubt teh eamk pu fo .mseen Fmor eht crreashe I fo,und as as tetdas lwobe by ,oy ceufstro si eth mots mtiontrpa stentcutoni of emesn in rmtes or rmspe cftuinno. loweB si torfminoain I udnfo ot edssadr het hrote answer ecohisc.

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,lylFnai I d'nto thkin het -lh5apa asteerudc ymzene is ayuactll ni ,smeen ubt I cldou eb n.rogw ritEeh way, it n'odtulw eb rlmayalbon delaevet or lwo if het seoostnetert vllees are on.alrm




 +0 
submitted by apurva(68),

Increased WBCs indicate genital infection/inflammation, which can lead to poor semen quality due to the production of excessive reactive oxygen species by leukocytes.

Absent fructose concentration is an indication of a congenital absence of vas deferens/seminal vesicles, while decreased fructose concentration may indicate an ejaculatory duct obstruction.

pH > 8.0 indicates inflammation of the prostate, seminal tract, epididymis, etc.; pH < 7.2 indicates seminal vesicle dysfunction or obstruction of the ejaculatory ducts.