Introduction: Characteristically the discordant thyroid function test has been attributed to TSH-producing hypophyseal adenoma, familial dysalbuminemic hyperthyroxinemia and thyroid hormone resistance syndrome. We presented 2 cases with raised peripheral thyroid hormones with detectable TSH due to the presence of auto-antibodies against the peripheral thyroid hormones (PTAAb).
|TSH (EQLA)||FT4 (EQLA)||FT4 (CMIA)||AAcT4 (%125I-T4)||FT3 (EQLA)||FT3 (CMIA)||AAcT3 (%125I-T3)||Sub-α (IRMA)||SHBG (QLA)|
|nv||0.384.84 μU/ml||0.82 ng/dl||0.71.48 ng/dl||<1.6%||1.84.6 pg/ml||1.713.71 pg/ml||<2%||00.9 mU/ml||11124 nmol/l|
Subjects and methods: A 24-year-old woman (1) and a 79-year-old woman (2) with auto-immune primary hypothyroidism diagnosed 4 and 3 years ago, with symptoms and signs of clinical hypothyroidism and without levothyroxine treatment was referred to our centre after a finding of discordant thyroid function values (Table). Hormonal and radioimmunoprecipitation studies. Subunit-α was determined by IRMA (Immunotech de Beckman Coulter©), SHBG by QLA (Immulite 2000 (DPC©), TSH was determined by EQLA, following series dilution (1/2, 1/5) of the sample. Samples were sent to another laboratory for determination of TP by two-step immunoassay (CMIA, Architect (Abbott Lab©). TPAAb was determined by incubating samples with I125-T4 and I125-T3, followed by precipitation in polyethyleneglycol. Precipitate count was obtained using a gamma-counter (Packard Cobra). Euthyroid patients with no auto-immune pathology were used as controls.
Results: The presence of PTAAb was detected in both cases (table), confirming the initial diagnosis of primary hypothyroidism.
Conclusion: The presence of PTAAb is an unusual cause of discordant thyroid function values that it must have in mind to the correct management of thyroid disease.
03 - 07 May 2008
European Society of Endocrinology