24.7 Path: Hormone measurement and interpretation Flashcards
If we have low thyroxine and low TSH, where is there a problem?
In the pituitary gland
If we have low thyroxine and high TSH where is there a problem?
Underactive thyoid
If we have high thyroxine and low TSH where is there a problem?
Overactive thyroid
What can we pick up to test early thyroid disease?
High TSH (thyroxine takes a while to have noticeable clinical symptoms)
What is an example of dynamic testing used in suspected diabetics?
Glucose tolerance
What can we use to test an increased cortisol level? What should this do?
Dexamethasone (should suppress cortisol, if not=Cushing’s)
What can we use to test low cortisol?
Synacthem (should increase cortisol)
What can we use in GH testing? (stimulation test and suppression)
Stimulation: exercise or hypoglycaemia (use if e.g. dwarf)
Perform GTT (GH should be supressed. Use if e.g. giantism)
What are the two types of immunoassays?
Competitive
Non competitive (sandwich)
How does a competitive immunoassay work?
Competition between an antibody and added labelled hormone
Measure how much label is attached
A small amount of label binds=a large amount of endogenous hormone
How does a sandwich immunoassay work?
Antigen is held between 2 antibodies (one is labelled)
Compare signal with standard graph
What are the pros/cons of using different antibodies to bind to a hormone that you wish to measure?
Polyclonal: strong binding, lack specificity
Monoclonal: weak binding, good specificity
What are 4 problems with assays?
Cross-reaction (ab may bind to another H)
Standardisation
Autoantibodies
Heterophilic assay (falsely high results)
