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DOI: 10.1055/s-0028-1094012
© Georg Thieme Verlag KG Stuttgart · New York
Congenital Goiter with Triiodothyronine as the Main Circulating Thyroid Hormone[*]
Publication History
Publication Date:
07 January 2009 (online)
Abstract
Serum triiodothyronine (T3) and TSH concentrations were determined in 4 siblings with congenital goiter. They were euthyroid, but had low serum thyroxine (T4) (1.7-3.0µg/100 ml; N: 5-12 µg/100 ml).
Serum T3 levels were normal or high (237-567 ng/100 ml; N: 150-270 ng/100 ml), while serum TSH concentrations were markedly increased (163-360 µU/ml). Since the absolute free T3 values were normal or near normal, the elevation of serum T3 observed in 3 of the 4 patients, was probably due to the increase in the binding capacity of serum thyroxine-binding globulin (TBG).
These findings indicate that T3 was the main circulating hormone in these patients and that they were maintained euthyroid by its serum levels, in spite of the low T4. They also suggest that TSH hypersecretion may result in a selective and preferential synthesis and/or secretion of T3. In this particular situation normal or near normal free T3 levels did not exert any significant inhibition of TSH release.
Key words
Goiter - T4 - T3 - Free T4 - Free T3 - TSH - TBG - TBPA - MIT - DIT
1 Supported by a Grant (MA-3943) from the Medical Research Council of Canada and by a Grant from the Medical Research Council of the Province of Québec.
1 Supported by a Grant (MA-3943) from the Medical Research Council of Canada and by a Grant from the Medical Research Council of the Province of Québec.