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NBME 24 Answers

nbme24/Block 2/Question#30 (29.1 difficulty score)
A 35-year-old man with small cell carcinoma ...
ACTH🔍
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 +16  upvote downvote
submitted by neonem(503),
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llSam ellc mairaconc of hte lnug mya puoedcr ptaapelsraocin sensmyod,r fo hihcw THAC nda ADH are teh mero mnomco yp.seustb AHCT sxscee dlsea ot cxsese mattsuoinil no the reldaan cerxot ot eudcpor t,croisol nsteilugr 'Cugnssih nyme.srdo Escxse ciosltor (rllamyno a estrss erh)onom cseusa hrneiyostenp aiv ntiteoaopitn fo yecphsmatti mniuattsiol on teh vsaueultcr.a It anc soal aeucs ayoemiakphl yb gtcain as a oeiitniomlorarcdc hnwe ni e,xecss nrastiguta het tlyabii fo x-orhdoeyd-a1rbsteyit1 odegaryedhnse etrp(sne in het alrne s)ueultb ot crotenv orisoclt to eo,ticonsr hwchi entsod' act as a ecraomc.trloiniido

therealslimshady  Adding some ways to eliminate the other answer choices for good measure: B) ADH can be secreted by small cell lung cancer (SCLC), and would cause SIADH, but that does not manifest with hypertension or hypokalemia. C) Epinephrine can cause hypertension (a1 effect), and hypokalemia (via stimulation of the Na/K-ATPase), but is secreted by pheochromocytomas rather than SCLC. D) PTHrP does not cause hypertension or hypokalemia, and is secreted by squamous cell carcinoma of the lung, not SCLC. E) VIP can cause hypokalemia through diarrhea (see VIPomas in First Aid), but not hypertension, nor is secreted by SCLC. +4  



  • SIADH → euvolemic hyponatremia → normotensive / hypertensive
  • ACTH increases cortisol → hypertension (alpha-1 upregulation & cortisol can bind to aldosteron receptors at high concentrations)
  • ACTH increases aldosterone → hypertension + hypokalemia (K+ dumped in collecting duct)

If patient -only- had hypertension: ACTH more likely than SIADH.

Patient with hypertension AND hypokalemia: 100% ACTH.

Don't feel bad friends, I also had this question wrong :(...

rolubui  ACTH does NOT act directly on the zona glomerulosa to increase Aldosterone. ACTH acts only on the zona fasciculata to increase cholesterol and zona reticulata to increases sex hormones. +2  
rolubui  NOT cholesterol I mean cortisol in zona glomerulosa +  



 +2  upvote downvote
submitted by famylife(77),
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oT ruel uto DHSAI eypt: m"Seru tsmouisap crcnnoaettion enyrlaleg ramnesi hugnn.eadc oeemtvnM fo tpisoausm omrf teh alliulneatrrc espca to the aecrlaxlurtel speca nereptvs dnlaouliti oy.peaihkmal sA ndhryoeg soin vmoe ecnliulytrara,ll tehy aer dncxgehae rfo mspsuoiat ni edrro to imnaaint retotla"e.nrylictue

/cehrpnsroress3pm/i-oafe--hris0ltwcouopitpumece-desm-mdn--he8nrmeoio-ayos3sesl-ieamidtnrfseci.r8o-a-/t.rso-tspwf5eiwe/dw4da:au6otht/2annw6tsvecap-

usmile1  Does anyone know if SIADH is associated with hypertension? I don't think it is due to the body's response of downregulating aldosterone, but if someone could verify that I would appreciate it. +  
sunshinesweetheart  @usmile1 pg 579 FA 2019 = BP can be normal or high in SIADH +  
usmlecrasherss  in SIADH GOLJAN says you have diluteonal hypokalemia +  
tyrionwill  SIADH -> excessive ADH -> water retention -> atrium excretes more ANP, ventricule excretes more BNP -> water is excreted more. So that is why not too much plasma volume increment, resulting mostly normal BP. +  



epi = pheochromocytoma of adrenal medulla = episodic HTN PTHrP = squamous cell carcinoma of lung (plus others) = hypercalcemia VIPoma = neuroendocrine pancreatic tumor =secretory diarrhea [WDHA (watery diarrhea, hypokalemia, achlorhydia]




 +0  upvote downvote
submitted by shiv360(0),

Aldo is primarily regulated by ATII. Cortisol is primarily regulated by ACTH. However, since cortisol can also activate aldo secondarily, it works. However, I believe that ADH should not have been answer choice however since no lung biopsy findings were reported so we can't really distinguish between SCC vs. NSCLC

misterdoctor69  the question literally says small cell carcinoma though +