374 Neurohypophysis

Question 1

What are the two hormones produced by the posterior pituitary

Answer 1

ADH

oxytocin

Question 2

syndrome associated with production of large amounts of dilute urine

Answer 2

diabetes insipidus

Question 3

average threshold for AVP release

Answer 3

osmolality of 280 mOsm/L or 135 meq/L

Question 4

what can lower the osmoregulatory system in AVP release

Answer 4

pregnancy, menstrual cycle, estrogen, relatively large, acute reductions in blood pressure or volume

Question 5

what is the physiologic action of AVP

Answer 5

reduce water excretion by promoting concentration of urine

Question 6

reduce water excretion by promoting concentration of urine

Answer 6

water diuresis

Question 7

where is the thirst center

Answer 7

anteromedial hypothalamus

Question 8

how is oxytocin different from AVP in chemical structure

Answer 8

differ only at positions 3 and 8

Question 9

decrease in AVP that results in diabetes insipidus

Answer 9

decrease of 75%

Question 10

urine volume and osmolality in diabetes insipidus

Answer 10

urine more than 40 cc/kg in 24 hr and osmolality of less than 300 mOsm/L

Question 11

also known as primary deficiency of AVP

Answer 11

neurohypophyseal DI, neurogenic DI, pituitary DI, central DI

Question 12

mutation in the WFS1 gene leading to diabetes insipidus, diabetes mellitus, optic atropahy, neural deafness

Answer 12

Wolfram syndrome

Question 13

causes nephrogenic DI

Answer 13

mutations in the AQP2 gene

Question 14

Urinary frequency, nocturia, enuresis. Volume less than 40 ml/kg. Osmolality more than 300 mOsm/L. Consideration?

Answer 14

GU evaluation

Question 15

Urinary frequency, nocturia, enuresis. Volume more than 40 ml/kg. Osmolality less than 300 mOsm/L.What next?

Answer 15

Basal AVP

Question 16

Urinary frequency, nocturia, enuresis. Volume more than 40 ml/kg. Osmolality less than 300 mOsm/L. Basal AVP less than 1 pg/ml

Answer 16

Brain MRI. Check for pituitary bright spot.

Question 17

Urinary frequency, nocturia, enuresis. Volume more than 40 ml/kg. Osmolality less than 300 mOsm/L. Basal AVP more than 1 pg/ml

Answer 17

Nephrogenic DI

Question 18

Urinary frequency, nocturia, enuresis. Volume more than 40 ml/kg. Osmolality less than 300 mOsm/L. Basal AVP less than 1 pg/ml. Brain MRI absent bright spot. Diagnosis?

Answer 18

Pituitary DI

Question 19

Urinary frequency, nocturia, enuresis. Volume more than 40 ml/kg. Osmolality less than 300 mOsm/L. Basal AVP less than 1 pg/ml. Brain MRI present bright spot. Diagnosis?

Answer 19

Primary polydipsia

Question 20

difference between AVP and synthetic DDAVP

Answer 20

DDAVP has 3-4x longer duration of action

Question 21

in what ways can DDAVP be given

Answer 21

IV or SC injection, orally and nasal inhalation

Question 22

dose of DDAVP

Answer 22

1-2 ug qd or BID by injection; 10-20 ug BID by nasal spray; 100-400 ug bid or tid orally

Question 23

when does hyponatremia in DI occur

Answer 23

when urine is reduced to less than 10 ml/kg/day

Question 24

syndrome characterized by chronic or recurrent hypertonic dehydration

Answer 24

hypodipsic hypernatremia

Question 25

laboratory findings in SIADH

Answer 25

low normal BUN and creatinine, low plasma renin activity, normal serum potassium, high urinary sodium

Question 26

treatment of SIADH

Answer 26

restriction of total fluid intake; ADH receptor antagonist

Question 27

how is convivaptan given

Answer 27

20 mg IV over 30 mins followed by continuous infusion of 20 mg over 24 hr

Question 28

how is tolvaptan given

Answer 28

15 mg po and increasing to 30 mg to 60 mg at 24 hr interval depending on effect