FREE THYROXINE (FT4) AND FREE TRIIODOTHYRONINE (FT3) IN AUTONOMOUS THYROID NODULES

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Abstract
Total and free thyroid hormones (T3 [triiodothyronine], T4 [thyroxine], F[free]T3 and FT4), TSH [thyrotropin] and its response to TRH [thyroliberin] were determined in 63 patients affected by autonomous thyroid nodules. Mean concentrations of FT3 were significantly higher in hot nodules (suppressing extranodular tissue on the scan) as compared to warm ones, even in those cases where total T3 and T4 were within normal ranges (hot nodules, group as a whole: 8.8 .+-. 3.5 pg/ml; warm nodules: 5.3 .+-. 1.2; hot nodules with normal total T3 and T4 concentrations: 7.5 .+-. 3). Also, the clinical condition of thyrotoxicosis appeared to be correlated with FT3 concentrations (toxic patients, group as a whole: 9.6 .+-. 4.0 pg/ml; euthyroid patients: 6.8 .+-. 3.1; toxic patients with normal values of T3 and T4: 8.3 .+-. 2.8). The correlation of total and free thyroid hormone concentrations with the response of TSH to TRH was not significant.