Suppression of Thyroid Function by Seaweed “Kombu” (Laminaria japonica) Supplement Seen in a Patient with Alopecia Areata: A Case Report

A 36-year old woman with severe alopecia areata was treated by intravenous corticosteroid pulse therapy, resulting in complete remission a year later. At her visit to us for follow-up, we found her thyroid swelling while she did not feel any symptom indicative of thyroid abnormality. Careful history taking revealed that she had kept taking supplement of seaweed “Kombu” (Laminaria japonica) (1g rhizoid/day) by herself for a year. Results of blood tests were: free T3, 2.7 pg/ml (normal: 2.3-4.3 pg/ml); free T4, 0.7 ng/ml (normal: 0.9-1.7 ng/ml) and TSH, 27.5 μU/ml (normal: 0.55.0 μU/ml) in the serum. Thyroid echo imaging revealed weight of thyroid as 28.68 g, which is larger than normal (8-20 g). Collectively, we diagnosed her as having thyroid suppression by iodine of the seaweed supplement and therefore advised her to prohibit its intake. Two months later, her blood tests showed normalization of thyroid hormone synthesis.