Posterior pituitary function

Question 1

ADH effects

Answer 1

distal tubules and CDs of kidney to reabsorb water

Question 2

ADH control

Answer 2

stimulated by: osmolality >290
decreased BV
nausea, stress, sleep exercise
drugs (nicotine, morphine, barbiturates)

inhibited by:
hypoosmolality
cold
drugs (alcohol, glucocorticoids)

Question 3

ADH deficiency

Answer 3

diabetes insipidus
polyuria, polydipsia, nocturia
genetic mutation of AVP-neurophysin gene, or acquired
Hypernatremia usually compensated by polydipsia
Central DI: decreased release from pituitary
Nephrogenic DI: ADH receptor on kidney
Treatmetn: drugs that enhance action/ADH analogues in severe disease

Question 4

SIADH causes

Answer 4

excess ADH release from pituitary
ectopic ADH secretion from tumour (pancreatic, bronchogenic, duodenal)
exogenous DAVP
increased ADH releasing agent, e.g. chlorporpamide

Question 5

SIADH consequences

Answer 5

dilutional hyponatremia, reduced chloride and urea, normal bicarb and optassium
urine osmolality higher than serum osmolality
symptoms due to fluid overload in brain causing confusion, irritability, ataxia, drowsiness, coma, death

Question 6

SIADH tx

Answer 6

fluid restriction
diuretics
remove ectopic source
slowly make changes otherwise water will move out of brain too quickly –> brain shrinkage

Question 7

Oxytocin function

Answer 7

role in sexual reproduction, particularly during and after hcildbirth
released in large amounts after distension of the cervix and uterus during labour, facilitating birth
and after stimulation of the nipples –> facilitates breastfeeding