Relationship between thyroid volume and serum thyroglobulin during long-term suppression with triiodothyronine in patients with diffuse non-toxic goitre

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Abstract
Twenty-five patients with non-toxic diffuse goitre were studied during and after 12 months of treatment with 60 μg triiodothyronine daily in order to see whether a correlation could be found between the reductions of thyroid volume, using ultrasonic scanning, and serum thyroglobulin. Thyroid function tests and thyroid volume determination were performed before treatment and after 3, 6 and 12 months of therapy in 19 patients (group 1). In patients of group 2 (n = 19) the same tests were performed at the end of 12 months treatment and 6 and 12 months after withdrawal. Before treatment all patients had a significantly increased thyroid volume compared to controls matched according to sex, age and body weight (P < 0.001). Serum thyroglobulin was elevated compared to controls (P < 0.02), with a significantly positive correlation to the thyroid volume (Spearmann's Rho = 0.52, P < 0.02). Both serum thyroglobulin and thyroid volume decreased during treatment in the majority of the patients, concomitantly in approximately half of them. After withdrawal of treatment (group 2) serum thyroglobulin showed a median increase of 54% after 6 months and remained unchanged thereafter, whereas the thyroid volume was unchanged after 6 months. These findings might support the concept that the regulation of thyroid growth and of protein synthesis and degradation might be determined by different factors.