Evaluation of thyroid function in patients with thyroid hormone autoantibodies

Antibody interference in thyroid assays: a potential for clinical misinformation

Measurements of thyrotropin and of total and free thyroxine and triiodothyronine are widely used diagnostic methods for thyroid function evaluation. However, some serum samples will demonstrate a nonspecific binding with assay reagents that can interfere with the measurement of these hormones. Several recent case reports have described the presence of such interferences resulting in reported abnormal concentrations of thyroid hormones inconsistent with the patient’s thyroid state. Circulating thyroid hormone autoantibodies, described in thyroid and nonthyroid disorders, are an important class of interference factor and can bind to hormone tracers used in various immunoassays. Two additional categories of interfering antibodies may particularly interfere within two-site immunoassays for thyrotropin. These include heterophile antibodies, especially human anti-mouse antibodies, and rheumatoid factors, which can cause interferences by immunoglobulin aggregation and (or) cross-linking of both capture and signal antibodies. Here we review the nature of these disturbances; their occurrence, prevalence, and detection; and the clinical consequences of the failure to recognize such interference.

Patients with Hashimoto's disease treated with L-thyroxine and followed for three years

This study investigated the effectiveness of L-thyroxine management in 32 patients (mean age 11 years and 2 months; M:F = 1:5) with Hashimoto's disease followed annually for 3 years. One (8%) of the 12 patients, euthyroid at the onset, never required treatment; of the four (33%) who began treatment immediately, two were able to stop at the 1st or 2nd follow-up, whereas two had to continue. The other seven (59%) who did not begin treatment immediately had to start at the 1st, 2nd or 3rd follow-up. The findings in this small series suggest that hormone management may prove effective to a certain extent in euthyroid Hashimoto patients, primarily as a means of prevention.