[Detection of thyroid hormone antibodies using a radial immunodiffusion method]

Area of Science:

• Endocrinology
• Clinical Chemistry
• Immunology

Background:

• Thyroid hormone assays (T3, T4) can show discrepancies with actual thyroid function.
• Protein binding anomalies and autoantibodies are known causes of these discrepancies.
• Autoantibodies can lead to falsely elevated or decreased T3/T4 values depending on assay separation techniques.

Observation:

• A study investigated 105 preselected thyroid patients for T3 and T4 autoantibodies.
• Thyroxine (T4) and triiodothyronine (T3) autoantibodies were assessed using a radial immune diffusion technique.
• Serum samples were incubated with radiolabeled T3/T4 and applied to an anti-IgG immune diffusion disc.

Findings:

• T3 autoantibodies were identified as the cause of elevated free T3 (fT3) values in one euthyroid patient.
• This patient exhibited normal clinical status, TRH/TSH response, and peripheral tissue parameters.
• The remaining 104 subjects tested negative for both T4 and T3 autoantibodies.

Implications:

• T3 autoantibodies are a rare but identifiable cause of thyroid assay discrepancies.
• The radial immune diffusion method is a quick, suitable screening tool for detecting these autoantibodies.
• Accurate thyroid function assessment requires consideration of potential autoantibody interference.