A case of resistance to thyroid hormone with thyroid cancer.

Resistance to thyroid hormone (RTH) is an autosomal dominant hereditary disorder that is difficult to diagnose because of its rarity and variable clinical features. The magnitude of RTH is caused by mutations in the thyroid hormone receptor beta (TR beta) gene. We recently treated a 38-yr-old woman with RTH who had incidental papillary thyroid carcinoma. She presented with goiter and displayed elevated thyroid hormone levels with an unsuppressed TSH. She was determined to harbor a missense mutation of M310T in exon 9 of the TR beta gene, and diagnosed with generalized RTH. This mutation has not yet been reported in Korea. RTH is very rare and easily overlooked, but should be considered in patients who present with goiter and elevated thyroid hormone levels with an unsuppressed TSH. The association between thyroid cancer and RTH needs further study.