A radioimmunoassay for human thyroglobulin: methodology and clinical applications

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Abstract
A specific double-antibody radioimmunoassay [RIA] with a sensitivity of 2.5 ng/ml was developed for measuring thyroglobulin (Tg) in human serum. As endogenous anti-Tg antibodies in serum interfere in the assay, only sera with a negative tanned red cell (TRC) test were suitable for analysis. Tg was detectable in 84.7% of the euthyroid subjects, with a mean value of 6.1 (values ranging from nondetectable to 43.0 ng/ml). Values were significantly higher in women than in men. Tg release by the thyroid appeared to be under pituitary control, as suggested by TSH [thyroid stimulating hormone] stimulation and T3 [triiodothyronine] suppression tests. Elevated Tg levels were found in hyperthyroidism, simple goiter and differentiated thyroid carcinoma. The significance of circulating Tg and the possible application of the Tg RIA are discussed.