SIADH

Question 1

What are the effects of ADH?

think permeability

Answer 1

1. increase H2O permeability in late distal tubule collecting ducts
2. increased activity of Na K 2CL transporter enhancing counter current multiplication
3. Increase urea permeability in inner medullary collecting ducts

Question 2

What is the normal regulation of ADH?

what are levels controlled by?

Answer 2

ADH levels are almost entirely controlled by plasma osmolarity

Question 3

What levels cause a significant shift in ADH levels?

Answer 3

volume change of 10% or greater

Question 4

What triggers ADH secretion to maintain volume

Answer 4

shock (severe volume loss)

Question 5

What is produced in SIADH

three things

Answer 5

1. hyperosmotic urine
2. hypoosmotic plasma
3. abnormally high ADH levels
   (you’re inhibiting the feedback mechanism)

Question 6

What is SIADH?

Answer 6

ADH is secreted independently of osmoreceptors

Question 7

What do higher ADH levels increase?

basically what does ADH do?

Answer 7

Water reabsorption in distal tubule and collecting duct

Question 8

What are SIADH causes?

Answer 8

ADH is secreted from areas that don’t respond to the feedback mechanism.
Lung tumors (secrete ADH), head injuries, and some drugs can cause this (typical/atypical antipsychotics like Haldol).

Question 9

What are the treatments for SIADH?

Answer 9

1. treat hyponatremia first, then the root cause second. DO NOT CORRECT SODIUM RAPIDLY.
2. First line tx: fluid restriction
3. second line tx: Vaptons (vasopressor receptor antagonists) if fluid restriction ineffective after 24-48 hours
4. Finally, treat the root cause

Question 10

Know normal response to water deprivation and drinking water.

Answer 10

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Question 11

review the case study

Answer 11

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