Familial dysalbuminemic hypertriiodothyroninemia: a new, dominantly inherited albumin defect.

We report the abnormal albumin in members of a Thai family that presented with high serum total T3 but not T4 when measured by radioimmunoassay. In contrast, total T3 values were very low when measured by ELISA and chemiluminescence. The subjects have no goiter, and clinically euthyroid. Their serum free T4, free T3, and TSH were normal. Spiking of T3 to affected serum showed good recovery by radioimmunoassay, but very poor recovery by ELISA and by chemiluminescence. The immunoprecipitation with labeled T3 bound to albumin showed high percent precipitation in affected serum. T3-binding studies showed that the association constant of serum albumin in affected subjects was 1.5 x 10(6) M-1 or 40-fold that of unaffected relatives of 3.9 x 10(4) M-1. In contrast, the Ka of HSA for T4 in an affected subject was only 1.5-fold that of a normal. Albumin complementary DNA from leukocytes of affected member was amplified and sequenced. We found the second nucleotide of normal codon 66 (CTT), a thymine, was substituted by a cytosine (CCT), resulting in the replacement of the normal leucine by proline. This is the first report of variant albumin causing familial dysalbuminemic hypertriiodothyroninemia.

Simple and sensitive test for thyroid hormone autoantibodies.

We presented a simple and sensitive test for thyroid hormone autoantibodies. The normal range for T4 and T3 autoantibodies in Thai people considering mean +/- 3 S.D. were 1.8-9.4 per cent and 3.1-8.6 per cent, respectively. Although positive low titer of thyroid hormone autoantibodies had almost no interference of thyroid hormone levels, high titer might cause great interference. This method can be used for screening patients who have unexpectably high levels of serum T4, T3 or discrepancy between thyroid hormone levels and clinical findings.

Lack of association between a polymorphism of human thyrotropin receptor gene and autoimmune thyroid disease.

A polymorphism in codon 52 of the human thyrotropin receptor results in a proline to threonine substitution in the extracellular domain of the receptor, but the association with autoimmune thyroid disease has been uncertain and there is no report the prevalence of this polymorphism in Orientals. To investigate this polymorphism and the association with autoimmune thyroid disease, we studied 113 normal unrelated individuals, 142 autoimmune thyroid disease patients including 112 Graves' disease and 30 Hashimoto's thyroiditis in the Thai population. We screened genomic DNAs of these subjects for the presence of A253 by PCR amplification using a degenerate oligonucleotide primer which produces a Tth111 I restriction site only in the presence of A253. The variant allele was present in 5.3 per cent of normal and 3.5 per cent of autoimmune thyroid disease, 2.7 per cent of Graves' disease and 6.7 per cent of Hashimoto's thyroiditis. The allele distribution in autoimmune thyroid disease patients did not differ significantly from that observed in controls. No association was found between this TSH-R polymorphism and the occurrence of autoimmune thyroid disease.