Transient thyrotoxicosis in endemic goitre patients following exposure to a normal iodine intake.
Twenty-three endemic goitrous subjects (goitre grade: III and IV) that were living in a chronic iodine-deficient area (iodine intake: less than 40 micrograms I/d) were submitted to clinical and laboratory evaluation within 3-8 weeks of arrival at the metropolitan area of São Paulo, where daily iodine intake is estimated to be 150-200 micrograms I/d. Eight patients developed a mild thyrotoxic state (T4 = 14.7 +/- 2.3 micrograms/dl, T3 = 279 +/- 55 ng/dl, no TSH response to TRH). Five additional subjects, although euthyroid, had a blunted TSH-response to TRH, and the remaining ten patients were euthyroid and had a normal TSH response to TRH. Thyrotoxicosis was associated with larger goitres (mean thyroid weight: 133 +/- 46 g), with high thyroid uptake of RAI (mean 24 h 131I uptake: 40 +/- 15%) but not with increased urinary iodine excretion. Serum Tg levels were more elevated in the first two groups of patients (respectively, geometric means 68 and 72 ng/ml), than in the euthyroid, TRH-responsive group (52 ng/ml). Thyrotoxicosis resolved spontaneously after three to six months without the need for any specific medication. It was concluded that a relatively small and normal iodide intake due to regular consumption of iodized salt and industrialized foods may induce a transient form of thyrotoxicosis in endemic goitre patients arriving into urban areas.
D000328:Adult; D004032:Diet / Q000009:adverse effects*; D005260:Female; D006043:Goiter, Endemic / Q000097:blood / Q000150:complications*; D006801:Humans; D006980:Hyperthyroidism / Q000209:etiology*; D007455:Iodine / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D013954:Thyroglobulin / Q000097:blood; D013960:Thyroid Function Tests; D013972:Thyrotropin / Q000097:blood; D013973:Thyrotropin-Releasing Hormone; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
D014284:Triiodothyronine; D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin; D013954:Thyroglobulin; D007455:Iodine; D013974:Thyroxine