Endocrine Testing

Question 1

OGTT

Answer 1

oral glucose tolerance test: DM insulin response

Question 2

GnRH stimulating test

Answer 2

for central precocious puberty: normal prepub won’t have raised LH in resposne; post-pub or CPP would

Question 3

Suppression test

Answer 3

• negative feedback by cortisol on ACTH secretion: dex (dexamethasone suppression test) for Cushing’s disease/syndrome
• Dex is potent glucocorticoid analogue and will attenuate ACTH secretion and thus cortisol in a healthy hypothalamic-pit axis
• Pts with Cushing disease:
  
  • have higher than normal threshold for negative fb on ACTH for cortisol
  • low-dose dex: cortisol remains high in Cushing’s pts
  • high-dose dex: knock down cortisol in a bit in most pts with Cushings disease
    
    • if positive, go check for a tumor
• Pts with Cushing syndrome:
  
  • ​high dose dex: may not reduce ACTH in event of ectopic ACTH produciton or otherwise exogenous ACTH
• -Cushing syndrome: any abnormal elevation in cortisol
• -Cushing disease: elevation in cortisol bc pit adenoma; ACTH excess

Question 4

What would make you suspicious someone has hypercortisolism?

Answer 4

• hyperglycemia
  
  • also:
    
    • Cushings
    • Acromegaly
    • DM1, DM2
• obesity
• muscle wasting
• stria on skin, bruising
• bone wasting