The Significance of Triiodothyronine (T3) in Maintenance of Euthyroid Status after Treatment of Hyperthyroidism

Abstract

Of 18 consecutive patients with low serum T4 after therapy for thyrotoxicosis, six appeared frankly hypothyroid on clinical grounds, whereas 12 appeared to be euthyroid. The normal metabolic status was considered to be dependent upon T3 concentrations. Serum TSH determinations by radioimmunoassay revealed normal levels in three of the 12 sera and varying degrees of elevation in the other nine. It was considered possible that TSH hypersecretion may result in T3 release despite diminished T4 secretion after radiation treatment