374 Neurohypophysis Flashcards
What are the two hormones produced by the posterior pituitary
ADH
oxytocin
syndrome associated with production of large amounts of dilute urine
diabetes insipidus
average threshold for AVP release
osmolality of 280 mOsm/L or 135 meq/L
what can lower the osmoregulatory system in AVP release
pregnancy, menstrual cycle, estrogen, relatively large, acute reductions in blood pressure or volume
what is the physiologic action of AVP
reduce water excretion by promoting concentration of urine
reduce water excretion by promoting concentration of urine
water diuresis
where is the thirst center
anteromedial hypothalamus
how is oxytocin different from AVP in chemical structure
differ only at positions 3 and 8
decrease in AVP that results in diabetes insipidus
decrease of 75%
urine volume and osmolality in diabetes insipidus
urine more than 40 cc/kg in 24 hr and osmolality of less than 300 mOsm/L
also known as primary deficiency of AVP
neurohypophyseal DI, neurogenic DI, pituitary DI, central DI
mutation in the WFS1 gene leading to diabetes insipidus, diabetes mellitus, optic atropahy, neural deafness
Wolfram syndrome
causes nephrogenic DI
mutations in the AQP2 gene
Urinary frequency, nocturia, enuresis. Volume less than 40 ml/kg. Osmolality more than 300 mOsm/L. Consideration?
GU evaluation
Urinary frequency, nocturia, enuresis. Volume more than 40 ml/kg. Osmolality less than 300 mOsm/L.What next?
Basal AVP
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. Check for pituitary bright spot.
Urinary frequency, nocturia, enuresis. Volume more than 40 ml/kg. Osmolality less than 300 mOsm/L. Basal AVP more than 1 pg/ml
Nephrogenic DI
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?
Pituitary DI
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?
Primary polydipsia
difference between AVP and synthetic DDAVP
DDAVP has 3-4x longer duration of action
in what ways can DDAVP be given
IV or SC injection, orally and nasal inhalation
dose of DDAVP
1-2 ug qd or BID by injection; 10-20 ug BID by nasal spray; 100-400 ug bid or tid orally
when does hyponatremia in DI occur
when urine is reduced to less than 10 ml/kg/day
syndrome characterized by chronic or recurrent hypertonic dehydration
hypodipsic hypernatremia
laboratory findings in SIADH
low normal BUN and creatinine, low plasma renin activity, normal serum potassium, high urinary sodium
treatment of SIADH
restriction of total fluid intake; ADH receptor antagonist
how is convivaptan given
20 mg IV over 30 mins followed by continuous infusion of 20 mg over 24 hr
how is tolvaptan given
15 mg po and increasing to 30 mg to 60 mg at 24 hr interval depending on effect
