Laboratory Thyroid Tests: A Historical Perspective

Area of Science:

• Clinical Chemistry
• Endocrinology
• Laboratory Medicine

Background:

• Thyroid disease impacts approximately 10% of the U.S. population, driving a significant portion of endocrine laboratory testing.
• Traditional thyroid tests were manual, time-consuming, and utilized radioactive iodine (e.g., ¹³¹I, ¹²⁵I) in nuclear medicine settings.

Approach:

• This review traces the historical development of laboratory thyroid tests over seven decades.
• It highlights key technological advancements, including radioimmunoassay and monoclonal antibody technology.
• The evolution from isotopic to nonisotopic immunometric assays performed on automated platforms is detailed.

Key Points:

• Modern thyroid testing relies on nonisotopic immunometric assays, a significant shift from earlier methods.
• Methods for measuring total and free thyroid hormones (thyroxine, triiodothyronine), TSH, thyroid autoantibodies, and thyroglobulin are discussed.
• Despite advancements, current tests face challenges including between-method variability and interferences.

Conclusions:

• Ongoing advancements have improved sensitivity and specificity in thyroid function tests.
• Future efforts focus on eliminating interferences and standardizing assays to establish universal reference ranges.
• Harmonization of thyroid tests is crucial for consistent patient management in outpatient settings.