A radioimmunoassay for human thyroglobulin: methodology and clinical applications.

A specific double-antibody radioimmunoassay with a sensitivity of 2.5 ng/ml has been 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 are 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 appears to be under pituitary control, as suggested by TSH stimulation and T3 suppression tests. Elevated Tg levels were found in hyperthyroidism, simple goitre, and differentiated thyroid carcinoma. The significance of circulating Tg and the possible application of the Tg RIA are discussed.