Iodide-induced hypothyroidism in a patient with anorexia nervosa.

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Abstract
A 39-year-old woman who had been suffering from anorexia nervosa was found to have hypothyroidism. Serum T4, free T4, T3, free T3 and TSH were 3.19 .mu.g/dl, 0.5 ng/dl, 15.3 ng/dl, 1.2 pg/ml and 162.1 .mu.U/ml, respectively. On careful questioning, she was found to have taken an iodine-rich diet. The serum iodine concentration was 122 .mu.g/dl (normal: 4-9 .mu.g/dl) and urinary iodide excretion was 13.05 mg/day (normal: less than 2 mg). After withdrawal of the iodine-rich diet, her serum T4 gradually increased and TSH returned to the normal range. She was diagnosed as having iodide-induced hypothyroidism. However, no significant elevation of serum T3 or free T3 was observed. Serum T4, free T4, T3, free T3 and TSH were 7.85 .mu.g/dl, 0.8 ng/dl, 13.6 ng/dl, 4.3 pg/ml and 6.02 .mu.U/ml, respectively. The iodide-perchlorate discharge test result was negative. These findings suggest that there exists some unknown mechanism by which a patient with anorexia nervosa may be sensitive to excess iodide. Furthermore, it is of interest to note that in a recovery phase from the hypothyroid state, normalization of serum T4 rather than T3 is well correlated to TSH secretion.