Diabetes Insipidus

Question 1

Osmoregulation with negative water balance

Answer 1

Either decreased [H20] or high plasma osmolality –> osmoreceptors –> secrete ADH from posterior pituitary –> increased H20 reabsorption –> increased [H20] and decreased plasma osmolality

Question 2

Osmoregulation with positive water balance

Answer 2

Either increased [H20] or decreased plasma osmolality –> osmoreceptors –> no secretion of ADH from posterior pituitary –> decreased water reabsorption –> decreased [H20] and increased plasma osmolality

Question 3

Central vs Nephrogenic DI

Answer 3

Central = no secretion of ADH --> no concentration of urine and polydipsia and polyuria
Nephrogenic = ADH cannot act on kidney tubules (either not responsive or no receptors) --> make sure adequate hydration and limit salt

Question 4

Clinical presentation of DI

Answer 4

Polyuria
Polydipsia
Nocturia

Question 5

Rehydration therapy

Answer 5

Oral if able!!!! –> pedialyte or gatorade, something ion balanced (not chicken broth, milk, or juice)
IV - 1/2 normal saline or 5% dextrose (500-1000 mL/hr)

Question 6

Central Diabetes Insipidus Treatment

Answer 6

Desmopressin and adequate hydration
Carbamazipine - stabilizes inactivated Na channels
Thiazides - stimulates gradient for reabsorption

Question 7

Nephrogenic Diabetes Insipidus Treatment

Answer 7

test by giving desmopressin, but desmopressin won’t do anything for treating nephrogenic DI
Stop Lithium, limit salt
Give Amiloride –> blocks ENaC, Li uses this channel too so you are stopping Lithium
Indomethacin –> blocks PGE2 –> constriction of afferent arteriole –> decreased RPF

Question 8

Action of ADH

Answer 8

ADH binds to V2 receptor –> adenylyl cyclase converts ATP to cAMP –> converts inactive PKA to active PKA –> converts CREB + ATP to CREB-P + ADP –> increased transcription of AQP-2