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MLAB 2401: Clinical Chemistry Keri Brophy-Martinez. Assessment of the Thyroid. 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
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MLAB 2401: Clinical ChemistryKeri Brophy-Martinez Assessment of the Thyroid
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
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
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
Thyroid Testing Methods • Competitive binding techniques • RIA • ELISA • FIA
Thyroid Antibodies • Thyroglobulin antibodies • Anti-thyroglobulin antibodies are mostly IgG and do not fix complement • Titerable using an indirect hemagglutination assay • Found in • Hashimoto’s thyroiditis • Grave’s disease • Subacute thyroiditis • Thyroid cancer
Thyroid Antibodies • Microsomal antibodies • Complement fixing IgG directed against a microsomal antigen within follicular cells • Found in • Hashimoto’s disease • Thyrotoxicosis • Primary myxedema