[A case of iodide myxedema observed for 3 years under a low iodide diet--especially on the restoration of the mechanism of escape from the Wolff-Chaikoff effect].

A 47-year-old housewife was admitted to our hospital because of general fatigue and constipation suggesting hypothyroidism. For 3 years before admission, general fatigue, arrhythmia, dry skin, drowsiness, cold intolerance and hypermenorrhea occurred insidiously. She had habitually taken considerable amounts of seaweed every day, e.g. more than 50 g of " Kombu " for more than 5 years and at least 1 g of " Wakame " for 6 months. On admission, serum thyroxine (T4) was 1.3 micrograms/dl, serum triiodothyronine (T3) was 47 ng/dl, TSH was 132 microunits/ml, and 123I thyroidal uptake was 60% at 3 hr. and 75% at 24 hr. Anti-thyroglobulin hemagglutination antibodies and anti-thyroid microsomal hemagglutination antibodies were both negative. When seaweed was omitted from her diet, T4 rose to 6.3 micrograms/dl and T3 rose to 113 ng/dl, whereas TSH lowered to 11 microunits/ml in 2 weeks. The seaweed-free diet was continued and 4 months later, when she had become euthyroid, an open biopsy of the thyroid gland was carried out. Histological examination of the specimen revealed a marked colloid deposition without characteristic features of Hashimoto's disease. Five months after admission, with the daily administration of 100 mg potassium iodide (KI), the effects of inorganic iodide on thyroid function had begun to be seen. On the 16th day of the KI regimen, palpitation and tachycardia (pulse rate 160/min.) with multifocal ventricular premature beat appeared, and T4 on the 11th day was 5.9 micrograms/dl, which was clearly lower than the pretreatment level of 8.4 micrograms/dl. KI was discontinued on the 16th day, and one week after the withdrawal, T4, T3 and TSH all returned to the pretreatment level. For more than 3 years on a seaweed-free diet, she remained euthyroid without any thyroid regimen. To see the effects of inorganic iodide on thyroid function after this long period on a seaweed-free diet, KI was again administered. One hundred mg/day KI for 14 days followed by 200 mg/day for 21 days had virtually no effect on T4, T3 and free T4 and she remained well. None of the perchlorate discharge tests performed on 3 occasions during the 6 month period after the initiation of the seaweed-free diet showed a discharge.(ABSTRACT TRUNCATED AT 400 WORDS)