Iodide-Induced Hypothyroidism in a Patient with Anorexia Nervosa

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 3.19μg/dl, 0.5ng/dl, 15.3ng/dl, 1.2pg/ml and 162.1μU/ml, respectively. On careful questioning, she was found to have taken an iodine-rich diet. The serum iodine concentration was 122μg/dl (normal: 4-9μ/dl) and urinary iodide excretion was 13.05mg/day (normal: less than 2mg). 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 7.85μg/dl, 0.8ng/dl, 13.6ng/dl, 4.3pg/ml and 6.02μU/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 wellcorrelated to TSH secretion. © 1986, The Japan Endocrine Society. All rights reserved.