Thyroid Gland: Lab Flashcards
Difficulties in Interpreting Thyroid Function Tests
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- as seen in hospitalized px with acute psychiatric illness
- due to medications
presence of abN° binding proteins (congenital or drug-induced)
alterations in hormone metabolism:
Hormone Measurements
• TRH
• TSH
• free T4
• free T3
Hormone Measurements
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- assays for this is not clinically useful
- difficult to develop specific antibody for an immunoassay
TRH measurement
Hormone Measurements
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- can identity virtually all instances of hyper- and hypothyroidism, except when:
• Damage to hypothalamus or pituitary gland
• Thyroid hormone resistance
• Interference with normal functioning of HPT axis due to medication
TSH measurement
Hormone Measurements
• TSH measurement
- can identity virtually all instances of hyper- and hypothyroidism, except when:
• Damage to hypothalamus or pituitary gland
• Thyroid hormone resistance
• Interference with normal functioning of HPT axis due to medication
TSH measurement
reference range:
0.5 - 5.0 microunits per milliliter (µU/mL)
Microinternational Unit per Liter
TSH measurement
- immunoassay
• first-generation assay
• second-generation assay
• third-generation assay
• fourth-generation assay
• RIA
• not sensitive enough
first-generation assay
• TSH measurement
- first-generation assay
• RIA
• not sensitive enough
• improved sensitivity (0.1 - 0.2 mU/L)
• monoclonal or polyclonal antibodies
second-generation assay
• TSH measurement
- second-generation assay
•improved sensitivity (0.1 - 0.2 mU/L - milliunits/ liter)
• monoclonal or polyclonal antibodies
• TSH measurement
• refinements in immunometric method
• sensi: 0.005 mU/L
• now common in use
- third-generation assay
• TSH measurement
- third-generation assay
• refinements in
• sensi:
• now common in use
immunometric method
0.005 mU/L
TSH measurement
• recently developed
• sensi: 0.0004 mU/L
• not widely available
- fourth-generation assay
TSH measurement
- fourth-generation assay
• recently developed
• sensi:
• not widely available
0.0004 mU/L