THYROTOXICOSIS FACTITIA (ALIMENTARY THYROTOXICOSIS): ITS DIFFERENTIATION FROM SPONTANEOUS THYROTOXICOSIS WITH THE AID OF RADIOACTIVE IODINE

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Abstract
Two cases of secretly self-induced thyrotoxicosis (thyrotoxicosis factitia) are described. The differential diagnosis between thyrotoxicosis factitia and endogenous thyrotoxicosis was facilitated by the use of tracer doses of radioactive iodine. In endogenous thyrotoxicosis the urinary excretion of radio-active iodine is lower than in euthyroid individuals but in thyrotoxicosis factitia the excretion of radioactive iodine is higher than normal. The serum protein-bound iodine is elevated in both conditions and therefore not contributory to the differential diagnosis. The combination of elevated serum-protein bound iodine and high excretion of radioactive iodine may also appear in endogenous thyrotoxicosis which is under treatment with thiouracil or iodide before the thyrotoxicosis is controlled. It may also appear after admn. of iodine containing dyes such as those used for cholecystrograms and pyelograms.