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Autoantibodies to thyroxin and triiodothyronine
R K Desai1, B Bredenkamp, I Jialal
1S.A. Medical Research Council, Preclinical Diagnostic Chemistry Research Unit, Congella, R. S. A.
Clinical Chemistry
|May 1, 1988
Summary
Thyroid hormone antibodies can cause falsely high free thyroxine (FT4) and free triiodothyronine (FT3) levels in euthyroid patients. Suspect these antibodies when thyroid function tests conflict with clinical presentation.
Area of Science:
- Endocrinology
- Immunology
- Clinical Chemistry
Background:
- Multinodular goiter can present with normal thyroid hormone levels.
- Standard thyroid function tests may yield inaccurate results in certain conditions.
Purpose of the Study:
- To investigate the presence and impact of thyroid hormone antibodies.
- To identify a potential cause for discordant thyroid function test results.
Main Methods:
- Assay of free thyroxine (FT4) and free triiodothyronine (FT3) concentrations.
- Detection of thyroid hormone antibodies using polyethylene glycol precipitation assay.
- Measurement of antithyroglobulin antibodies.
Main Results:
- Two euthyroid patients with multinodular goiter showed high FT4 and FT3 levels.
- Thyroid hormone antibodies were detected in these patients, but not in healthy volunteers.
- Antibodies were also found in some hyperthyroid and hypothyroid patients, often alongside antithyroglobulin antibodies.
Conclusions:
- Thyroid hormone antibodies can lead to falsely elevated FT4 and FT3 measurements.
- Discordant thyroid function tests and clinical status warrant investigation for thyroid hormone antibodies.
- Sensitive thyrotropin assays can aid in accurate thyroid status determination in such cases.