Low Thyroidal T₃ in Nodular Goitrous Tissue

Summary

Six nodular tissues of non-treated and four of treated patients (suppressive treatment with thyroid hormones from three months to two years until the operation) with nodular non-toxic goitre contained low T₃ (< 1 ug/g w.w.).

The results of iodothyronines and thyroglobulin (Tg) were compared with respective tissues containing T₃ > 1 ug/g w.w. In non-treated patients, nodular tissues with low T₃ and very high T₄/T₃ ratio showed T₄ and Tg concentrations not different from the tissues with T₃ > 1 ug/g w.w. In the goitres with low T₃ of treated patients, T₄ was also reduced but disproportionately to T₃.

Microscopically, nodular goitres with low T₃ were characterized with gross fibrous infiltration and diffuse haemorrhage which was substantially different from histological findings in nodular goitres with T₃ > 1 ug/g w.w.

High T₄/T₃ ratio in the tissues with low T₃ is similar to increased T₄/T₃ ratio in paranodular tissues of autonomously functioning adenomas.

The results suggest that low T₃ and high T₄/T₃ ratio in nodular goitrous tissue could be due to grossly impaired thyroid function or due to suppressed secretion of TSH.

Key-Words:

Non-Toxic Goitre - Thyroidal Iodothyronines - Thyroidal T₄/T₃ Ratio