MLAB 2401: Clinical Chemistry Keri Brophy-Martinez

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MLAB 2401 Clinical ChemistryKeri Brophy-Martinez

• Assessment of the Thyroid

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Historical Procedures

• Basal Metabolic Rate
• Measured rate of oxygen consumption over a 15
  minute period
• Required careful patient preparation and
  precision of testing
• Radioactive iodine uptake test
• Measured the ability of the thyroid to take up
  and trap iodine
• Rate of absorption is determined by measuring
  increased radioactivity in the thyroid gland

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Historical Procedures

• Protein bound iodine (PBI)
• Used to estimate the amount of thyroid T3 and T4
  by measuring the amount of iodine contained in a
  protein precipitate of serum

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Common Thyroid Function Tests

• TSH
• Total T3 and total T4
• Free T3 and Free T4
• T3 Uptake (for binding proteins)
• Free thyroxine index( estimate of Free T4)
• Serological testing for antibodies to thyroid
  disease

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Thyroid Testing Methods

• Competitive binding techniques
• RIA
• ELISA
• FIA

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Thyroid Antibodies

• Thyroglobulin antibodies
• Anti-thyroglobulin antibodies are mostly IgG and
  do not fix complement
• Titerable using an indirect hemagglutination
  assay
• Found in
• Hashimotos thyroiditis
• Graves disease
• Subacute thyroiditis
• Thyroid cancer

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Thyroid Antibodies

• Microsomal antibodies
• Complement fixing IgG directed against a
  microsomal antigen within follicular cells
• Found in
• Hashimotos disease
• Thyrotoxicosis
• Primary myxedema