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NBME 21 Answers

nbme21/Block 4/Question#6 (36.2 difficulty score)
A 55-year-old man comes to the physician ...

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submitted by beeip(116),
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isTh ahs neeb a ghtou ncecotp for me to tge, ubt I tkhin Im' ifyanll :teerh

heT mest is bgiicdrsne yrrpaim eanlard nisncyfc,iuefi or ni.odAds's

  • THAC si bneig dpveudoo-crer to atitusmel the rnleadsa ot oedcurp olirt,ocs btu hyte t'nac erpodn,s hieert ued to thrayop ro ioduentcstr ,T(B einota:umum ,4DR )t.ce
  • ehT ftsri 31 oainm ascid fo TAHC nac be lcaevde to form ,αHM-S hwhci ttsemulsai ta,cmeoenlys ugcnsai potinitpnehrgymae
jotajota94  Good job! Also, cortisol is involved in maintaining blood pressure. which was decreased in the patient. +7  
tinydoc  Decreased Na and increase K+ --- Hypoaldosteronisim Hypoglycemia, and hypotension --- Hypocortisolism so the adrenals arent working ---- adrenal Insufficiency the Hyperpigmentation comes from the increase ACTH as ACTH is from Proopiomelanocorticotropin. SO - increased ACTH also increases a -MSH ---> Hyper pigmentation. +10  
hungrybox  thank u for this answer +  
bilzcop  Ugh! I misread the question and chose ACTH :( +2  
cienfuegos  @bilzcop: same +  
cienfuegos  @bilzcop: let's never do it again, k? +1  
maxillarythirdmolar  Why does this patient have elevated BUN and creatinine?? +2  
lovebug  @ maxillaryhidmolar > I don't know exactly. but maybe.. Low hypo-adlo -> our body lose water -> hypo-volemia -> Decreased GFR -> Increased Cr,BUN. If I'm wrong. please correct me. +  

The stem is describing primary adrenal insufficiency, or Addison's.

ACTH is being over-produced to stimulate the adrenals to produce cortisol, but they can't respond, either due to atrophy or destruction (TB, autoimmune: DR4, etc.) The first 13 amino acids of ACTH can be cleaved to form α-MSH, which stimulates melanocytes, causing hyperpigmentation. Cortisol helps with BP and his is low.

Patients also have low aldosterone. Low Na and high K is a sign of hypoaldosteronism. Patients retain H and lose HCO3. Losing HCO3 causes Cl- retention in the PCT. This all leads to metabolic acidosis. Loss of cortisol causes anorexia, hypoglycemia, and a low BP as seen in this patient.