Endocrine - Online MedEd - Posterior pituitary

Question 1

2 hormones to consider posterior pituitary

Answer 1

oxytocin

ADH

Question 2

Syndrome of inappropriate ADH - pathophys

Answer 2

Lung lesion - extra ADH secretion - small cell lung cancer/pneumonia/granuloma
Brain secretes extra ADH - brain lesion
Body will reabsorb more water
Body knows it has too much water, so kidneys will turn off secretion of aldosterone
So that Na is excreted in the urine, because H2O follows Na

Question 3

What does ADH do

Answer 3

Tells nephron to absorb more water

Question 4

What happens to urine osmol and Na in SIADH?

Answer 4

Urine osmoles increases

Urine Na increases

Question 5

Patient presentation of SIADH

Answer 5

Serum osmoles that are low
Hyponatremia (will be hypotonic)
Usually asymptomatic

Question 6

Diagnostic step of SIADH

Answer 6

Urine Na, Urine osmoles, Serum osmoles

• Urine Na and Urine osmoles are elevated
• Serum osmoles decrease

Question 7

Treatment of SIADH

Answer 7

Water restriction

• Reverse underlying disease
• i.e. treat PNA, treat TB, resect tumour
• Get excess water back to urine –> give demeclocycline (induce diabetes insipidus)

Question 8

Diabetes insipidus - what is it?

Answer 8

Don’t have glucose in urine, nothing to do with glucose
Pathophys - ADH activates ADH receptors in kidneys normally. Diabetes insidious is not enough ADH. Central or nephrogenic (demeclocycline or lithium toxicity)
-Excess water in urine, Urine osmoles are low

Question 9

Central DI?

Answer 9

Break production of ADH

Question 10

Nephrogenic DI?

Answer 10

Break ADH receptor

Question 11

DI - diagnosis?

Answer 11

Water deprivation test

• Is this psychogenic polydipsia?
• Differentiate central with peripheral?
• Patient comes in with very dilute urine, so at some point in test, will stop allowing water
• If it was that they were drinking too much, ADH will kick in and urine osmoles will increase!
• But if there is a problem with ADH, will not be able to absorb water and the urine osmoles will still be low
• AT this point, give them ADH –> this is central DI!
• If give ADH, kidney can’t respond –> so nephrogenic

Question 12

Patient presentation of DI

Answer 12

Polydipsia
Polyuria
Normal blood glucose
No glucose in urine (DM - excess glucose in urine, which draws water out!)

Question 13

Treatment of DI?

Answer 13

Psychogenic - stop drinking so much water
Central DI - DDAVP
Nephrogenic DI - gentle diuresis use hydrochlorothiazide, amiloride