A study of thyroglobulin and peroxidase activity in the thyroid tissue of patients with non-endemic non-toxic nodular goitre.

1. A study was made of the activity of the enzyme thyroid peroxidase and of the concentration, carbohydrate composition and the degree of iodination of thyroglobulin in the thyroid glands of 60 patients with non-endemic non-toxic goitre in the nodular phase and in those of 25 control subjects. 2. Thyroid peroxidase activity was determined by the guaiacol assay and was significantly higher in patients with non-endemic non-toxic goitre than in control subjects (3.60 +/- 2.51 and 2.07 +/- 1.08 mumol of guaiacol oxidized min-1 g-1 of tissue, respectively; ranges 0.16-10.57 and 0.52-4.85 mumol of guaiacol oxidized min-1 g-1 of tissue, respectively; P less than 0.05). 3. Thyroglobulin was purified by precipitation with ammonium sulphate and Sephadex G-200 gel filtration. Two protein peaks were obtained which were identified as thyroglobulin and measured by radioimmunoassay. The concentration of thyroglobulin in the first peak was 98.94 (SD 84.87, range 0.60-455.54) mg/g of tissue for the patients with non-endemic, non-toxic goitre and 51.41 (SD 28.34, range 14.99-106.39) mg/g of tissue for the control subjects (P less than 0.01). The second peak showed 1.26 (SD 1.27, range 0.09-6.50) mg of thyroglobulin/mg of tissue for the group with non-endemic non-toxic goitre and 0.51 (SD 0.25, range 0.15-0.98 mg of thyroglobulin/mg of tissue) for the control subjects (P less than 0.01). 4. The carbohydrate composition of thyroglobulin was determined by acid hydrolysis and colorimetry, evaluating the levels of hexoses, hexosamines and sialic acid.(ABSTRACT TRUNCATED AT 250 WORDS)