OnlineMedEd: Endocrine - "Posterior Pituitary"

Question 1

In __________, the urine osmolarity increases.

Answer 1

SIADH

Question 2

Why does urinary sodium increase in SIADH?

Answer 2

SIADH causes increased water retention in the kidneys. This leads to fluid overload. The body responds by turning off aldosterone secretion. Low aldosterone states lead to increased urinary sodium.

Question 3

Small cell carcinoma and _____________ lesions can cause SIADH.

Answer 3

brain

Question 4

How is SIADH treated?

Answer 4

• Water restriction
• Treat the disease that is causing it
• Demeclocycline if the above fail to treat it

Question 5

What pair of urinary labs suggests SIADH?

Answer 5

Increased UNa and UOsm

Normally, if the UOsm increases it is because water is pulled into the blood with sodium, and thus UNa decreases. The increase in both of these is suggestive of SIADH.

Question 6

Diabetes insipidus presents with __________ UOsm.

Answer 6

decreased

Question 7

Explain the patient presentation of DI.

Answer 7

• They present with polydipsia and polyuria.
• You test their urine or blood for hyperglycemia and it is negative. UOsm will be low.
• Hospitalize them for a water deprivation test. If they continue to have low UOsm for several hours into water deprivation, then they have DI. Give ADH to determine if it is NDI or CDI.

Question 8

Review the treatments for psychogenic polydipsia, central DI, and nephrogenic DI.

Answer 8

• PP: stop excess water intake
• CDI: give DDAVP
• NDI: give gentle diuresis with amiloride to trigger other parts of the nephron to absorb water