Abstract
Introduction: Resistance to thyroid hormone is a syndrome caused by thyroid hormone receptor β mutations,
which are usually inherited in an autosomal-dominant pattern.
Case presentation: Our patient, a Japanese neonate boy, showed hyperthyroid symptoms at age two days.
Although our patient was diagnosed as having resistance to thyroid hormone, his hyperthyroid symptoms
continued for two weeks. Therefore, our patient was treated with methimazole and iodine for two weeks from
birth, showing no side effects and no symptoms upon treatment. At age 70 days, an R243W mutation in thyroid
hormone receptor β was detected in our patient; while absent in his mother, the mutation was present in his
father, who never showed any symptoms.
Conclusions: To the best of our knowledge this is the first case report of a resistance to thyroid hormone in a
neonate presenting with hyperthyroid symptoms born to a mother with Graves’ disease and treated with
methimazole and iodine. These results suggest that methimazole and iodine may be a good short-term option for
treatment.
Keywords: Hyperthyroid symptoms, Maternal Graves’ disease, Symptomatic neonate with resistance to thyroid
hormone, Treatment for resistance to thyroid hormone