Iodine‐induced thyrotoxicosis: analysis of eighty‐five consecutive cases

Publisher Website
Google Scholar
Abstract
I-induced thyrotoxicosis was documented in 85 cases. Eighty per cent occur in apparently normal thyroid glands; 60% among them occur in males. Amiodarone accounted for 50% of I-induced thyrotoxicosis. Mean thyroid hormone levels at diagnosis were: FT1 [free thyroxine index]: 21.7 (normal mean: 7.5, arbitrary units); T3 [triiodothyronine]: 4.53 nmol 1-1 (normal: 2.30 nmol 1-1). Mean 131I- 24-h uptake was 3.5% (normal range in France 25-45%) and was activated by exogenous TSH (mean 27%). The spontaneous cure in nontreated cases were observed within an average 6 mo. A phase of biological hypothyroidism (mean FT1: 3.7, T3: 1.23 nmol 1-1, TSH; 9.6 .mu.U ml-1 (normal TSH range: 1-7 .mu.U ml-1)) preceded the return to euthyroidism. Intrathyroid I content measured by x-ray fluorescence was high, then fell gradually. Thyroid tissue study showed a large quantity of intrathyroid I and the overiodination of thyroglobulin. Histological and EM studies are reported. Prednisone and in some cases propylthiouracil were found to be effective.