USMLE BIOCHEMISTRY

[@blapspblamaster]

Correct in theory but there is a mistake in the stem - phenylalanine restriction alone wouldn't get us past the PKU issue if there was one. That would be tyrosine supplementation.

[@parpar7878]

I still do not understand why the answer is not A...I need help

[@shsfehyr]

Because his phenylalanine restricted diet should result in no symptoms but he is still showing them so it’s c

[@crazysingerr]

Basically PKU Is due to either deficiency of Phenylalanine hydroxylase (most common )or deficiency of its cofactor BH4. Let’s say he is on a phenylalanine restricted diet so phenylalanine levels coming to normalcy, yet he is showing symptoms as in this case high prolactin levels….means to say the PKU is due to deficiency of BH4 …..as BH4 is also needed for conversion of tyrosine to dopa. Decreased dopamine increases prolactin. As dopamine is a natural inbitor of prolactin. Phenylalanine ➡️ tyrosine➡️ Dopa➡️dopamine ➡️Ne

[@ridsasim4685]

Thank you!!

[@aleenawaseem9970]

Excellent sample question and explanation 💫

[@RandyNeilMD]

Glad it was helpful!

[@aziznicola7674]

Thanks a lot🙏🏼 u r the best 🙏🏼

[@RandyNeilMD]

Thank you Aziz. KEEP STUDYING HARD!!

[@JayAnam1997]

Thankyou sir!

[@RandyNeilMD]

You are welcome.

[@derkies2133]

What Step exam is that? 2ck? Oder 1?

[@urjasanghvi5733]

Sir, why not dopamine carboxylate?

[@jamilaweatherly5376]

The dopamine carboxylase is less likely given the presentation. The patient is mostly demonstrating a PKU pattern . Basically since the diet was accounted for , the only other plausible deficiency is the DHR. The patient is already limiting the phenylalanine that would need to be processed. :)

[@elisha-doa-lereigh]

7 for 8 now 🤣 I should become a doctor

[@jameswadsoniloveyoujesusfo4429]

Answer is C

[@VcL13]

You can see from his writing he a doctor

[@RandyNeilMD]

KZbin won't let me dictate...

[@lostwizardcat9910]

yup didnt understand that shit. but uh...good job i think...

[@RandyNeilMD]

Thank you... I think.... well maybe

[@shirkhanaliev5794]

can you say why not 1

[@lostwizardcat9910]

@@shirkhanaliev5794 because biochemistry is complicated as all hell lol.

[@ezzatebrahim6337]

malignant pku