THYROID HORMONE interesting question! - USMLE Forums
USMLE Forums Logo
USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
Home
USMLE Articles
USMLE News
USMLE Polls
USMLE Books
USMLE Apps
Go Back   USMLE Forums > USMLE Step 1 Forum

USMLE Step 1 Forum USMLE Step 1 Discussion Forum: Let's talk about anything related to USMLE Step 1 exam


Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 06-15-2011
USMLE Forums Scout
 
Steps History: Not yet
Posts: 70
Threads: 5
Thanked 13 Times in 10 Posts
Reputation: 23
Thyroid THYROID HORMONE interesting question!

QUESTION

What is the "the source" and the "enzyme" to get rT3 ?

a) T4 - 5 deiodinase
b) T3 - 5´deiodinase
c) T3 - 5 deiodinase
d) T4 - 5´deiodinase
e) none of these
Reply With Quote Quick reply to this message
The above post was thanked by:
bebix (06-17-2011)



  #2  
Old 06-15-2011
dr z's Avatar
USMLE Forums Addict
 
Steps History: Step 1 Only
Posts: 136
Threads: 34
Thanked 349 Times in 89 Posts
Reputation: 369
Default D

D : T4, 5'deiodoniase
Reply With Quote Quick reply to this message
  #3  
Old 06-15-2011
qurat21's Avatar
USMLE Forums Master
 
Steps History: 1 + CK
Posts: 623
Threads: 62
Thanked 287 Times in 186 Posts
Reputation: 297
Default

Quote:
Originally Posted by dr z View Post
D : T4, 5'deiodoniase
i think its d
Reply With Quote Quick reply to this message
  #4  
Old 06-15-2011
USMLE Forums Scout
 
Steps History: Not yet
Posts: 70
Threads: 5
Thanked 13 Times in 10 Posts
Reputation: 23
Default

Lets wait for at least 1 day to offer the response/comment. Why? ...the is more than one answer. You´ll see. Hope to have Miss Patho or Bebix opinion BUT...no using books!.. only what they have on mind
Reply With Quote Quick reply to this message
  #5  
Old 06-15-2011
bebix's Avatar
USMLE Forums Master
 
Steps History: 1+CK+CS+3
Posts: 1,357
Threads: 194
Thanked 3,259 Times in 881 Posts
Reputation: 3269
Default

Quote:
Originally Posted by Chemole View Post
QUESTION

What is the "the source" and the "enzime" to get rT3 ?

a) T4 - 5 deiodinase
b) T3 - 5´deiodinase
c) T3 - 5 deiodinase
d) T4 - 5´deiodinase
e) none of these
I think is a)
source T4
enzime 5 deiodinase

...I only have one answer though
Reply With Quote Quick reply to this message
  #6  
Old 06-15-2011
USMLE Forums Guru
 
Steps History: Not yet
Posts: 417
Threads: 74
Thanked 129 Times in 93 Posts
Reputation: 139
Default

since t4 has iodine on 3,3',5,5'..
reverse rt3 has 3,3',5',,, and we have to remove iodine from 5 only therefore .. my ans is also A
Reply With Quote Quick reply to this message
  #7  
Old 06-15-2011
USMLE Forums Guru
 
Steps History: Not yet
Posts: 324
Threads: 70
Thanked 236 Times in 143 Posts
Reputation: 246
Default

Quote:
Originally Posted by Chemole View Post
QUESTION

What is the "the source" and the "enzime" to get rT3 ?

a) T4 - 5 deiodinase
b) T3 - 5´deiodinase
c) T3 - 5 deiodinase
d) T4 - 5´deiodinase
e) none of these
hmm..
Source is T4..
enzyme will be 5'deiodinase..
So i would go with D..
Reply With Quote Quick reply to this message
  #8  
Old 06-16-2011
USMLE Forums Scout
 
Steps History: Not yet
Posts: 70
Threads: 5
Thanked 13 Times in 10 Posts
Reputation: 23
Correct Answer Answer "a" correct

OK GUYS, thanks for ur attention. Here I offer the comment, rather than the response.

I choosed also D when I saw this, initially. It would mean that T4 is the source and the enzime for getting RT3 is 5´deiodinase. BUT...

From different sources I got different answers.
Pass Program says we get RT3 directly from T3 and using a 5 deiodinase (not prime ´ !!!).
U-World says that we get RT3 from T4 using 5´deiodinase but they are not that clear when explaining it.
In other sources you find that from T4 and thanks to 5´deiodinase you get your loved T3 (the standard active form)...but they dont say clearly if for getting RT3 you use 5´deiodinase or 5 deiodinase (not prima).
On internet, in very specialized sites you find that T4 becomes T3 (active form) thanks to 5´ deiodinase and that RT3 is result of a change in the 5´ towards a 5 not prime.

There are interesting data also, like... 5´deiodinase and its dependence of Selenium and Zinc. Mainly Selenium. Also that the pathway of conversion from T4 to T3 can be diverted to RT3 in relation to any kind of stress (or change in cortisol levels, too high or too low)

I finally think that if we get a scenario (in the step 1) with a question that make us consider these dat...a we should consider that T4 is converted by 5´deiodinase to T3 and that RT3 comes from T4, ok, BUT..using a very similiar deiodinase, without PRIME ´ . For the guy that said this is low yield...., i would say that problems with RT3 are common and understimated and undertreated. I have 10 years as doctor, that is why I tell u this My intention is to show how you can find very different data over there. Now, if somebody is against this....we will thank you a lot if you explain it more.

T4 ------------------------T3
5´deiodinase

T4-------------------------RT3
5 deiodinase (not prime)

Thanks for your attention, dear Forum
You guys perhaps have other better documentd sources. I bet u is again different
Reply With Quote Quick reply to this message
The above post was thanked by:
7802 (06-16-2011), leo lakhani (06-16-2011)
  #9  
Old 06-16-2011
USMLE Forums Guru
 
Steps History: Not yet
Posts: 404
Threads: 108
Thanked 71 Times in 48 Posts
Reputation: 80
Default

Quote:
Originally Posted by Chemole View Post
OK GUYS, thanks for ur attention. Here I offer the comment, rather than the response.

I choosed also D when I saw this, initially. It would mean that T4 is the source and the enzime for getting RT3 is 5´deiodinase. BUT...

From different sources I got different answers.
Pass Program says we get RT3 directly from T3 and using a 5 deiodinase (not prime ´ !!!).
U-World says that we get RT3 from T4 using 5´deiodinase but they are not that clear when explaining it.
In other sources you find that from T4 and thanks to 5´deiodinase you get your loved T3 (the standard active form)...but they dont say clearly if for getting RT3 you use 5´deiodinase or 5 deiodinase (not prima).
On internet, in very specialized sites you find that T4 becomes T3 (active form) thanks to 5´ deiodinase and that RT3 is result of a change in the 5´ towards a 5 not prime.

There are interesting data also, like... 5´deiodinase and its dependence of Selenium and Zinc. Mainly Selenium. Also that the pathway of conversion from T4 to T3 can be diverted to RT3 in relation to any kind of stress (or change in cortisol levels, too high or too low)

I finally think that if we get a scenario (in the step 1) with a question that make us consider these dat...a we should consider that T4 is converted by 5´deiodinase to T3 and that RT3 comes from T4, ok, BUT..using a very similiar deiodinase, without PRIME ´ . For the guy that said this is low yield...., i would say that problems with RT3 are common and understimated and undertreated. I have 10 years as doctor, that is why I tell u this My intention is to show how you can find very different data over there. Now, if somebody is against this....we will thank you a lot if you explain it more.

T4 ------------------------T3
5´deiodinase

T4-------------------------RT3
5 deiodinase (not prime)

Thanks for your attention, dear Forum
You guys perhaps have other better documentd sources. I bet u is again different

i found nothing about this in kaplan,...nor did kobrak mention about it!!!where did u guys get this?
Reply With Quote Quick reply to this message
  #10  
Old 06-17-2011
dr z's Avatar
USMLE Forums Addict
 
Steps History: Step 1 Only
Posts: 136
Threads: 34
Thanked 349 Times in 89 Posts
Reputation: 369
Thumbs Up chemical structure

U r right , i just looked up to the chemical structure of T4 T3 rT3 in kaplan 2010
first ring is all prime and second ring is no prime
if v compare T3 with rT3
the diff is T3 has no I at 5'
while rT3 has no I at 5 (no prime)

now this makes sence to me, thanks
Reply With Quote Quick reply to this message



Reply

Tags
Endocrine-, Physiology-

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the USMLE Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Medical School
Choose "---" if you don't want to tell. AMG for US & Canadian medical schools. IMG for all other medical schools.
USMLE Steps History
What steps finished! Example: 1+CK+CS+3 = Passed Step 1, Step 2 CK, Step 2 CS, and Step 3.

Choose "---" if you don't want to tell.

Favorite USMLE Books
What USMLE books you really think are useful. Leave blank if you don't want to tell.
Location
Where you live. Leave blank if you don't want to tell.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Thyroid Problem Question meka USMLE Step 1 Forum 7 06-15-2011 06:59 PM
Thyroid question fernandbteich USMLE Step 1 Forum 3 06-15-2011 04:16 PM
Here is an interesting case! chamarezka USMLE Step 2 CK Forum 5 03-17-2011 11:13 AM
Interesting Associations atr88 USMLE Step 2 CK Bits & Pieces 1 12-10-2010 09:03 AM
Interesting question HouseWannabe USMLE Step 1 Forum 12 06-15-2010 07:12 PM

RSS Feed
Find Us on Facebook
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.

USMLE® & other trade marks belong to their respective owners, read full disclaimer
USMLE Forums created under Creative Commons 3.0 License. (2009-2014)