T3 toxicosis and its relation to the iodide status in Singapore

Baseline thyroid function tests (including total serum thyroxine iodide-T4I, total serum tri-iodothyronine T3 as well as T3 Sephadex Uptake Studies (T3U)) were determined in 82 normal Asian subjects. In addition, another group of normal volunteers (39) were assessed as regard serum and 24-hour urinary iodide levels to gauge the iodide status of the community; the results were comparable to that of goitre-free regions of the world. Having established the range of values of normal thyroid function tests, 103 consecutive clinically thyrotoxic patients (both new and relapsed cases) were similarly studied in an attempt to elucidate the magnitude of the problem of T3 toxicosis, and its relation to the iodide status in Singapore. Only three clinically hyperthyroid patients were foudn to have normal PBI T3 levels. A detailed analysis and discussion of the data is presented. It is concluded that T3 toxicosis is a rarity in Singapore.