Investigation of Thyroid Flashcards
How do we measure hormones in blood?
Immunoassay
What are the different types of Immunoassay?
Competitive immunoassay
immunometric assay
What does a competitive imunoassay use?
A limited amount of antibody and is used for small molecules such as thyroid hormones or steroid hormones
How does a competitive immunoassay work?
Add a limited amount of antibody and the sample and incubate. These will then try to competitevely bind to the receptor. You then wash out whatever is not bound.
The bound lable is inversely proportionate to analyte concentration - the more T4 in the sample the more it will outcompete and the lower the signal.
immunometric assay
uses antibody excess and used for large peptides such as peptide hormones or proteins.
in an immunometric assay what is used to increase specificity?
monoclonal antibodies
How deos an immunometric immunoassay work?
You need the capture antibody bound to the side of the test tube. This antibody can bind to the analyte.
Another antibody (labelled antibody) can then bind to the other side of the analyte - this will only bind to samples.
The higher the analyte the more signal
what are the possible ways the immunoassay can be configured?
Capture antibody - beads, magenetics, plastics, microlitre plate, fibre strip
Label antibody - radiolable, chemiluminescent, flourescence, enzyme linked,
Why would you use a thyroid function test?
Establish a thyroid dysfunction and monitor treatment
What thyroid measurements would you want to test for?
TSH
free T4/T3
Hyperthyroidism specific = TSH Receptor Ab
Hypothyroidism specific = Anti-TPO Ab
Should you measure both TSH and T4 together to get to the source of the problem?
Yes
Hypothyroidism test what would you expect the biochemical tests to look like?
Low T4 and high TSH
Hypopituitarism test what would you expect the biochemical tests to look like?
Low T4, normal or low TSH (the TSH is less active by loosing glycolysation)
Biochemical test results of primary hypoparathyrodism?
High TSH
Low T4
Normal or low T3
Biochemical test results of secondary hypothyroidism?
Low TSH or normal
Low T4
Low of normal T3
Hypethyroidism test what would you expect the biochemical tests to look like?
High TSH
High FT4 and FT3
biochemical test results primary hyperthyroidism?
Low TSH
High T4 and T3
Biochemical test results for secondary hyperthyroidism? This is rare
High or normal TSH
High T4 and T3
What is more senstive TSH or T4?
TSH for every 4x increase in T4 TSH drops by 10x
What would the biochemical results be for someone who is sub clincal hyperthyroidism?
T4 high for you but “normal” as it is in the range but TSH is switched of?
T3 normal
What would the biochemical results be for someone who is sub clincal hyporthyroidism?
Normal T4 and T3 but low TSH
How would you know if the sub clinical disease is trying to become over disease such as graves?
Thyroid antibodies
what is panhypopituitarism?
when your pituatiry gland is not right
What is Non-thyroidal illness
Intercurrent illness can affect functioning of pituirary thyroid axis
Can lead to difficulty interpreting the results of thyroid functional tests.
Can acute illness - pneumonia upset the TSh and T4 levels?
Yes
What can cause reduced TSH?
Malnutrician, illness or stress
What can stress, illness and malnutrician do to deoidinase type 2?
Reduce this increasing production of rT3 which means you can’t treat these people with T4 as it will just turn into rT3
In acute hospital setting what would a low TSH probably be?
Twice as likely to be a non-thyroidal illness as hyperthyroidism
In acute hospital setting what would a raised TSH probably be?
As likely to be due to recovary from illness as hypothyroidism
What must TFTs be interpreted alongside?
interpreted alongside clinical findings
