Biochemistry Flashcards
sodium exists in which fluid compartment?
ECF
AVP is another word for…
ADH
what does aldosterone do?
retains Na in an effort to retain water
the Na in a dehydrated urine sample would be low/high
low
describe the H20 and Na in SIADH
high H20 low Na (kidneys trying to get rid of sodium because of low water)
what substances can mimic hyponatraemia and cause pseudohyponatraemia?
higher proteins and lipoproteins
patient with really low Na who is fine…
pseudohyponatraemia
decreased blood volume stimulates the release of what substances
aldosterone
ADH
renal excretion of sodium is a key mechanism by which the kidneys regulate blood volume T or F
T
what test distinguishes between central and nephrogenic DI?
DDAVP
name the mechanism by which ADH regulates water conc
countercurrent multiplication
what is DDAVP?
exogenous ADH
nephrogenic/central DI will not respond to DDAVP
nephrogenic
what is the problem in primary adrenal sufficiency?
cant make mineralocorticoids eg aldosterone so low Na
ADH causes inc water absorption/excretion
absorption
ADH also acts on what structures other than kidneys?
blood clotting
anxiey stress
blood vessel constriction and dilatation
how much steroid do you need to regulate the HPA axis per day
7.5mg
patients with what condition are less likely to retain Na than other subjects
primary adrenal insufficiency eg addisons
ACTH only acts on the cortex T or F
T
commonest cause of addisons
autoimmune
synacthen test measures…
give ACTH and see if cortisol levels increase
how can you determine between primary and secondary adrenal sufficiency?
measure ACTH levels
parathyroid glands stimulate DIRECT Ca absorption where?
bone
kidneys
parathyroid glands stimulate Ca absorption INDIRECTLY where? how does it do this?
gut via vitamin D
secondary hyperparathyroidism results from pitiitary stimulation of the parathyroid glands T or F
F! pituitary has no control over parathyroid
hypercalcaemia interferes with absorption where in the kidney? what happens as a result?
PCT
low Na
most common cause of hyperkalaemia
renal failure
then haemolysis then drugs eg spirinolactone
what is the main difference appearance-wise of SIADH compared to hyponatraemia
patient won’t be dry
first line Tx SIADH
fluid restriction
diagnostic features of SIADH
“wet” patient
high urine osmolality
Ix cushings syndrome
short and long synacthen test
Ix cushings disease
dexamethasone suppression test
what level is the hallmark of tumour lysis syndrome?
high urate
