Hormone measurement and interpretation Flashcards
describe thyroid hormone mechanism of release and feedback
hypothalamus releases TRH on pituitary—–>pituitary releases TSH on thyroid—->thyroid releases thyroxine (T4)—> T4 feedback inhibits pituitary
78 yr old female presents with weight gain and feeling tired. Query: hypothyroidism?
Blood analysis report:
TSH= 52 mIU/L
T4 unbound= 3.5 pmol/L
What is the Suspected site of dysfunction?
Ref intervals:
TSH (0.4 - 4.7 mIU/L)—>High
T4 (9-25 pmol/L)—>Low
consistent with hypothyroidism due to thyroid dysfunction
42yo male presents with feeling tired and slow. appears pale.
Query: hypothyroidism
Blood analysis report:
TSH= 0.01 mIU/L
T4 unbound= 2.7 pmol/L
What is the Suspected site of dysfunction?
Ref intervals:
TSH (0.4 - 4.7 mIU/L)—>Low
T4 (9-25 pmol/L)—>Low
Consistent with hypothyroidism due to pituitary dysfunction.
on thyroid function tests, a low TSH and high T4 (thyroxine) would indicate [….]
overactive thyroid
Ref intervals:
TSH (0.4 - 4.7 mIU/L)
T4 (9-25 pmol/L)
on thyroid function tests, a low TSH and low T4 (thyroxine) would indicate [….]
underactive pituitary
Ref intervals:
TSH (0.4 - 4.7 mIU/L)
T4 (9-25 pmol/L)
on thyroid function tests, a high TSH and low T4 (thyroxine) would indicate [….]
under-active thyroid
Ref intervals:
TSH (0.4 - 4.7 mIU/L)
T4 (9-25 pmol/L)
if you can only choose one, the best indicator of failing thyroid gland is [….]
TSH.
it rises into abnormal levels well before fT4 (free thyroxane).
TSH usually compensates by amping up its levels to keep fT4 up.
in cases of subclinical disease, use of [….] testing is advantageous by driving pathological signs to manifest under stressed conditions.
Query: Underactiva gland—-> [..] it
Query: Overactive gland—> […] it
dyanamic
stimulate it
suppress it
suspected diabetes patients may under this dynamic test: [….].
Sustained high glucose at 2hr post-oral administration would be interpreted as [….]
glucose tolerance test (gold standard for detecting diabetes).
administer 75mg of glucose orally, then check glucose at 1 and 2 hrs post.
glucose intolerance —> diabetes
In suspected Cushing’s syndrome (hyperactive adrenal cortex), the dynamic test […..] would be used.
sustained levels of cortisol would indicate […..]
decreased levels of cortisol (
dexamethasone suppression test.
—>dex should suppress normal adrenal production of cortisol.
Ref: basal serum cortisol (250-750 nmol/L)
Post-dex (
in patients with suspected adrenal underactivity, the dynamic test […..] may be employed.
spiked cortisol (1800nmol/L) would indicate [……]
acth/synacthen stimulation test
synacthen 250ug IM at time 0. measure at 30min and 1hr. ——>Cortisol should spike to 1800 nmol/L.
indicate no adrenal suppression (normal).
if pituitary dysfunction is suspected, the dynamic test [……..] may be employed.
This involves admistering doses of 3 drugs: [….] and monitoring for 150 minutes.
–>albeit this test is very dangerous (why?).
combined pituitary function test
insulin (glucose levels), TRH , LHRH
risky, give the patient hyperglycaemia!!
in cases where growth hormone deficiency is suspects, a dynamic test [….] may be used.
the stimulus may be […..]
growth hormone stimulation test
exercise, hypoglycaemia, arginine
hormones with very low levels are best detected/quantified using the technique of [….], of which there are two predominant methods: [….] and […]
immunoassays
sandwich immunoassay (non-competitive) and competitive immunoassay
principle behind [….] immunoassay is that the competition between the specimen hormone and added labelled hormone for a limited amount of antibody.
A […known/variable…] amount of labelled hormone is added along with a volume of blood containing natural hormone of […known/variable…] amounts.
A standard curve of serial dilutions can reveal how well the tagged hormone can compete.
competitive.
known
variable
