Three Japanese patients from two families with generalized resistance to thyroid hormone with mutations in exon 9 of the thyroid hormone receptor beta gene

Resistance to thyroid hormone (RTH) is a genetic disorder caused by mutatio ns in the thyroid hormone receptor (TR) beta gene. The mutations are cluste red in two regions: exon 9 and exon 10. To date, only one patient with an e xon 9 mutation has been reported in Japan. We herein report three patients from two Japanese families with RTH and mutations in exon 9. A 52-year-old woman and her 18-year-old daughter, both with inappropriate secretion of TS H (SITSH) were diagnosed simultaneously with generalized RTH. Molecular ana lysis revealed a G345D mutation. An 11-year-old girl with SITSH, whose only manifestation was a goiter, had an R338W mutation, which is frequently ass ociated with pituitary RTH. Thus, RTH with mutations in exon 9 of the TR be ta gene is not so rare in Japan.