Effect of 8-anilino-1-naphthalene sulfonic acid (ANS) on the interaction between thyroid hormone and anti-thyroid hormone antibodies

Competitive immunoassays for simultaneous detection of metabolites and proteins using micromosaic patterning

New high-throughput immunoassay methods for rapid point-of-care diagnostic applications represent an unmet need and current focus of numerous innovative methods. We report a new micromosaic competitive immunoassay developed for the analysis of the thyroid hormone thyroxine (T4), inflammation biomarker C-reactive protein (CRP), and the oxidative damage marker 3-nitrotyrosine (BSA-3NT) on a silicon nitride substrate. To demonstrate the versatility of the method, both direct and indirect format competitive immunoassays were developed and could be applied simultaneously for single samples. Signals from standard solutions were fit to a logistic equation, allowing simultaneous detection of T4 (7.7-257.2 nM), CRP (0.3-4.2 microg/mL), and BSA-3NT (0.03-22.3 microg/mL). Total assay time including sample introduction, washing, and fluorescence measurement was less than 45 min. Dissociation constants for affinity pairs in the system have been estimated using regression. This proof-of-concept experiment shows that both small and macromolecular biomarkers can be quantified from a single sample using the method and suggests that groups of clinically related analytes may be analyzed by competitive micromosaic immunoassay techniques.

Prevalence of thyroid hormone autoantibodies in healthy subjects

OBJECTIVE

The prevalence of thyroid hormone autoantibodies in patients with thyroid disorders has been well described, although the results have been variable. However, the prevalence of thyroid hormone autoantibodies in apparently healthy subjects remains unknown and its determination was the main objective of this study.

SUBJECTS AND METHODS

Sera obtained from 880 healthy subjects (365 men and 515 women) were examined for thyroid hormone autoantibodies by immune precipitation using radiolabelled thyroid hormones or thyroid hormone analogues.

RESULTS

Anti-triiodothyronine (T3) and anti-thyroxine (T4) antibodies were detected in none (0%) and in 3 (0.34%), respectively, of the 880 individuals studied using radiolabelled thyroid hormones. Similar tests in 385 healthy subjects using radiolabelled thyroid hormone analogues (polyaminocarboxy T3 and T4) showed the presence of anti-T3 and anti-T4 antibodies in 3 (0.78%) and in 4 (1.04%), respectively. None of the subjects had both anti-T3 and anti-T4 antibodies. Thus, the prevalence of anti-T3 or anti-T4 antibodies among healthy population was concluded to be as high as 1.8%. Radiolabelled thyroid hormone analogue binding to purified immunoglobulin G (IgG), with or without the addition of an excess of unlabelled thyroid hormones, confirmed specific binding of thyroid hormones to the thyroid hormone autoantibody-positive IgGs. The presence and class specificity of thyroid hormone autoantibodies was confirmed by the Ouchterlony immunodiffusion/autoradiography method, which showed biphenotypic heavy chain (IgG and IgA) and kappa (kappa) light chain specificities. Serum concentrations of free thyroid hormones and TSH in thyroid hormone autoantibody-positive sera were within the normal range.

CONCLUSIONS

These results indicate that the occurrence of thyroid hormone autoantibodies among the healthy Japanese population is fairly common. However, interference of thyroid hormone autoantibodies in the radioimmunoassay of free thyroid hormones is exceptional.

Thyroid hormone autoantibodies in patients with Graves' disease: effect of anti-thyroid drug treatment

We examined the effects of anti-thyroid drug treatment on serum autoantibodies against thyroid hormones (thyroid hormone autoantibodies, THAA), thyroglobulin (Tg) and thyroid peroxidase (TPO) in patients with Graves' disease by measuring each autoantibody level before and after treatment. Six patients among 40 untreated patients with Graves' disease had anti-thyroxine (T4) antibodies. One patient had both anti-T4 and anti-triiodothyronine (T3) antibodies. Thus the prevalence of THAA in untreated Graves' disease was 7 out of 40 (17.5%). Changes in T4-Ab levels after treatment varied. In five cases (cases 3-7) levels decreased 4-7 months after treatment. However, in the other two cases levels fluctuated 1, 3, 6 and 12 months after treatment. None of the previously THAA-negative patients became positive after treatment. Anti-Tg antibody (Tg-Ab) was positive in 34 out of 40 (85%) untreated cases and its level decreased in both THAA positive and negative patients after treatment. Anti-thyroid peroxidase antibody (TPO-Ab) was positive in 32 of the 40 (80%) untreated Graves' patients and its level significantly decreased after treatment. Our findings suggest that treatment with anti-thyroid drugs does not produce THAA in Graves' disease.