Case of Thyroid Hormone Resistance Syndrome with a Mutation in the Thyroid Hormone Receptor Beta Gene

In thyroid hormone resistance syndrome (THR) TSH levels are normal or elevated despite thyroid hormone levels being elevated. THR is distinguished from TSH-producing pituitary adenoma by TRH stimulation and α-subunit tests, thyroid hormone receptor (TR) β gene analysis, and sellar MRI. A 24-year old man with diffuse goiter visited our hospital complaining of fatigue, heat intolerance, palpitation, and weight loss. He had elevated total T3 and free T4 levels, but normal TSH levels. Serum TSH levels during TRH stimulation tests performed before and after T3 suppression showed normal and non-suppressible responses, respectively. The serum basal α-subunit test result was normal. A TR β gene R438H mutation was identified, and a pituitary mass with cystic change was identified by sellar MRI. We report a case of THR with a mutation (R438H) in the TR β gene, the first case of its kind in Korea. (Korean J Med 2011;80:S220-S226)