[Radioimmunological determination of circulating thyroid hormones].

In our study of the thyroid function, the methodological aspects and clinical significance of TSH, T4, T3 and their respective free fractions (FT4 and FT3), are examined. The RIA of TSH is the best for the diagnosis of hypothyroidism and also for the evaluation of the effect of thyroid hormone substitution therapy. This, united with T4 and T3 assay, allows a total evaluation of the thyroid state. The new method, recently introduced, for direct assay of free fractions, using a chromatographic separation of Sephadex LH 20, is extremely useful for follow-up of patients with thyroid disfunction.