01b: Post Pit

Question 1

T/F: Both ADH and oxytocin are synthesized as large pro-hormones.

Answer 1

True

Question 2

Pro-hormone is enzymatically cleaved into ADH and (X). In the case of oxytocin, it’s cleaved into the active hormone and (Y).

Answer 2

X = Y = neurophysin

Question 3

AVP/ADH binds to renal (X) receptors and stimulates:

Answer 3

X = V2

cAMP/PKA (synthesis and insertion of AQP2)

Question 4

Supra-physiologic AVP can bind to (X) receptors and have which extra-renal effect?

Answer 4

X = V1 receptors (on vascular smooth muscle)

Increase BP

Question 5

List the four main mechanisms of AVP/ADH regulation

Answer 5

1. Osmoreceptors (ant hypothalamus)
2. Baroreceptors (atria)
3. Nausea
4. Thirst

Question 6

Baroreceptors located in (X) will (increase/decrease) AVP secretion when (Y) is decreased by 5-10%.

Answer 6

X = atria
increase
Y = blood V

Question 7

Nausea (increases/decreases) AVP secretion.

Answer 7

Increases (potently and rapidly)

Question 8

Max AVP release level is with plasma osm of:

Answer 8

295 mOsm/kg

Question 9

List the three main mechanisms behind DI.

Answer 9

1. Central DI (less AVP produced/released)
2. Gestational DI (increased metabolism of AVP)
3. Nephrogenic DI (resistance to AVP in kidney)

Question 10

T/F: In order for central DI to occur, the pituitary typically suffers a huge insult and loses 90% secretory capacity .

Answer 10

False - pituitary lesion alone insufficient; lesion must be in hypothalamus or stalk (with over 90% secretory capacity lost)

Question 11

Central DI: (abrupt/insidious) onset of (X) symptoms, with (Y) as the most objective symptom.

Answer 11

Abrupt
X = polydipsia, polyuria, thirst
Y = nocturia

Question 12

If patient has (adequate/restricted) water access, DI can cause which complications/presentation?

Answer 12

Restricted

Hypernatremia/hyperosm (mental status deterioration), hyperthermia, coma, brain shrinkage (vessel rupture)

Question 13

List the 3 most important causes of Central DI

Answer 13

1. Neurosurg/trauma
2. Tumors
3. Infiltrative disease

Question 14

List 3 tumors that commonly cause central DI.

Answer 14

1. Craniopharyngioma
2. Germinoma
3. Hypothalamic glioma

Question 15

After nsurg, pt that develops central DI will go through which phases of response?

Answer 15

1. Acute (low AVP)
2. Interphase (high AVP spill)
3. Permanent (low AVP)

Question 16

After 6 days post-op, patient with surg-induced central DI has sudden (rise/drop) in urine output. Is he cured/recovered from the DI?

Answer 16

Drop (interphase period of triphasic response);

Not necessarily

Question 17

List some causes for nephrogenic DI

Answer 17

Hypokalemia, hypercalcemia, Li use

Question 18

The classic etiology for primary polydipsia is (X).

Answer 18

X = schizophrenia (over-concerned with belief that water is healthy)

Question 19

Beginning an evaluation of DI involves first eliminating (X) diagnosis. Which labs do you order to accomplish this?

Answer 19

X = osmotic diuresis

1. Urine Osm
2. Serum Osm
3. Serum chemistry (electrolytes, glucose, Cr, Ca)

Question 20

The exact etiology of a patient’s DI can be separated from others by (X) test.

Answer 20

X = water deprivation

Question 21

T/F: Administration of DDAVP in water deprivation test will not affect the trajectory of increasing urine Osm in a normal individual.

Answer 21

True

Question 22

List the etiologies of DI that will have unaffected Urine Osm with DDAVP administration.

Answer 22

1. Nephrogenic

2. Primary polydipsia

Question 23

List the etiologies of DI that will show little to no (increase/decrease) in urine Osm with water deprivation alone.

Answer 23

Increase;

1. Nephrogenic
2. Complete central DI

Question 24

Hypertonic saline infusion can be used to diagnose (X) etiology of DI. You measure (Y). How would you expect (Y) levels to change?

Answer 24

X = Central DI
Y = AVP

No change in AVP
(unlike rise in AVP if etiology was primary polydipsia, or nephrogenic DI)