endocrine measurement Flashcards
why is it good to just measure TSH level when suspecting thyroid dysfunction
TSH levels start to increase early with only very slight/early thyroxine decreases
how can you tell whether low thryoxine is due to poor thyroid function of poor pituitary stimulation
poor thyroid function –> low thyroxine but high TSH
poor pituitary stimulation –> low thyroxine AND low TSH
why would you use dynamic testing on a patient
- to see what a system does under stressed conditions
- is an abnormal hormone result due to a physiological or pathological cause
how does the dexamethasone suppression test used for
to see if the adrenal gland is producing too much cortisol
how does the dexamethasone suppression test work
- patient takes dexamethasone at midnight
- this steroid should suppress normal adrenal production of cortisol
- measure cortisol before and after dexamethasone
what will the normal and abnormal results be for a dexamethasone test be
normal - low level of cortisol in the morning
abnormal - still high level of cortisol in the morning
what is the point of a synacthen stimulation test
to see if someone has adrenal underactivity/failure
explain the synacthen stimulation test
- stimulate the gland with ACTH and measure cortisol levels at various time intervals
what are the normal and abnormal responses of the synacthen stimulation test
normal - cortisol will rise rapidly and significantly
abnormal - no cortisol rise
what drugs do you inject into the patient who is having a combined pituitary function test
insulin –> measure drop in glucose and rise in cortisol and ACTH
TRH –> measure increase in tyroxine and prolactin
LHRH –> measure increase in LH and FSH
why do we use immunoassays to measure hormone levels
because the hormones are present only at very low levels and therefore require very sensitive measurement systems
two types of immunoassays used for hormone level measurement
competitive immunoassay - one antibody with labelled and natural hormone
noncompetitive immunoassay - two antibodies (one labelled) with natural hormone
explain the standard curve of the competitive immunoassay for hormone level measurement
the higher the natural hormone concentration, the lower the signal
explain the standard curve of the non-competitive immunoassay for hormone level measurement
the higher the natural hormone concentration the greater the signal
what are the pros and cons of using polyclonal and monoclonal antibodies
monoclonal - can have weak binding, good specificity
polyclonal - strong binding, may lack specificity
