Can't understand Dexamethasone suppression test - 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 11-01-2010
USMLE Forums Scout
 
Steps History: Not yet
Posts: 16
Threads: 3
Thanked 7 Times in 6 Posts
Reputation: 17
Unhappy Can't understand Dexamethasone suppression test

can any1 explain d mechanism behind d dexamethasone suppression test used to differentiate pituitary, adrenal n other ACTH producing conditions leading to cushing's syndrome......
I can't get why d cortisol level varies with dose in all these cases...too confusing....
Reply With Quote Quick reply to this message
The above post was thanked by:
Mariahadi (09-25-2014)



  #2  
Old 11-01-2010
USMLE Forums Guru
 
Steps History: 1+CK+CS+3
Posts: 363
Threads: 18
Thanked 312 Times in 149 Posts
Reputation: 322
Default

Quote:
Originally Posted by futureresident View Post
can any1 explain d mechanism behind d dexamethasone suppression test used to differentiate pituitary,adrenal n other ACTH producing conditions leading to cushing's syndrome......
i cant get why d cortisol level varies with dose in all these cases...too confusing....

ACTH controls Cortisol

Dexamethasone = "Super Cortisol"

Dexamethasone provides negative feedback to the pituitary to suppress the secretion of ACTH.

Low Dose test
--------------
Suppress:
1- Normal
2- Obese (adipose tissue preduces cortisol)
3- Depression (stress produces cortisol)

No Suppress after low dose- have Cushings, do a high dose test

High Dose Test "PAL"

Suppress:
Pituitary tumor- ACTH

Not Suppress:
1- Adrenal adenoma- Cortisol
2- Lung cancer- ACTH, SIDAH, cushings moon facies
Reply With Quote Quick reply to this message
The above post was thanked by:
futureresident (11-02-2010), Mariahadi (09-25-2014), rasheed (11-01-2010), Taiwan_Guy (05-16-2011)
  #3  
Old 11-01-2010
mtoi's Avatar
USMLE Forums Scout
 
Steps History: Not yet
Posts: 71
Threads: 30
Thanked 54 Times in 29 Posts
Reputation: 64
Default

Dexamethasone suppression test
screening tests for endogenous cushing syndrome include
overnight low dose dexamethasone suppression test
24-hr urine free cortisol
administration of dexamethasone, potent glucocorticoid, should suppress acth and cortisol levels in normal individuals
however, pts with endogenous cushing syndrome donít suppress serum cortisol levels following administration of low dose dexamethasone
typically, in pts with cushingís ds, cortisol levels donít suppress with low dose dexamethasone but do suppress with high-dose dexamethasone
the test is useful in differentiating cushing ds from cushing synd caused by ectopic acth production
when there is ectopic source of acth, acth levels are typically markedly elevated, and there is no suppression of acth or cortisol with even high-dose dexamthasone
Reply With Quote Quick reply to this message
The above post was thanked by:
futureresident (11-02-2010), Mariahadi (09-25-2014), rasheed (11-01-2010), Taiwan_Guy (05-16-2011)
 
  #4  
Old 11-01-2010
USMLE Forums Master
 
Steps History: 1+CK+CS+3
Posts: 742
Threads: 137
Thanked 2,460 Times in 441 Posts
Reputation: 2563
Arrow Some useful previous threads about Dexamethasone Suppression test

You may also find the following threads useful:
Reply With Quote Quick reply to this message
The above post was thanked by:
dr z (11-01-2010), futureresident (11-02-2010), Mariahadi (09-25-2014)
  #5  
Old 11-01-2010
dr z's Avatar
USMLE Forums Addict
 
Steps History: Step 1 Only
Posts: 136
Threads: 34
Thanked 350 Times in 89 Posts
Reputation: 370
Post Dexa Doses

(just to add on the discussion)
High dose dexamethsone means 8mg
Low dose dexamethsone means 1mg
source kaplan physio qbank.
Reply With Quote Quick reply to this message
The above post was thanked by:
dr pinky (01-16-2011), futureresident (11-02-2010), Mariahadi (09-25-2014), Taiwan_Guy (05-16-2011)



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
Dexamethasone Suppression Test steroidmd USMLE Step 1 Classic Clues 5 02-16-2017 08:59 PM
Dexamethasone Suppression Test donofitaly USMLE Step 1 Forum 6 09-05-2012 01:14 PM
I don't understand the number of chromosomes! Androide89 USMLE Step 1 Forum 6 08-31-2011 11:00 PM
Make me understand the NBME Forms Loyalty USMLE Step 1 Forum 1 09-14-2010 02:16 AM
Dexamethasone Suppression! hippocampus USMLE Step 1 Forum 4 01-13-2010 02:58 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)