An asymptomatic 14 year-old girl with thyromegaly had elevated serum T4(19.9 mg/dl), but normal TSH (0.9 μU/ml). Despite elevated T3, and free T4, serum TSH increased normally after TRH administration. Suppression of TRH-induced TSH release with 200 mg/day of L-T3 occurred as serum T3 rose to 788 ng/dl. Sequence analysis of her thyroid hormone β-receptor gene revealed a mutation at nucleotide 1330 (GTG→ATG) resulting in a Val→Met change at position 349 in exon 9.

To investigate attention deficit-like behavior described in RTH, 7 family members (4 affected) were administered tests of ability, achievement, reading, language and attention (WISC-III, WAIS-R, Woodcock-Johnson Revised Achievement Subsets, Rosner Auditory Analysis). RTH subjects appeared to have lower overall ability compared to unaffected relatives. RTH subjects manifested substantially impaired decoding skills, specifically letter word-identification and word-attack compared to unaffected relatives. However, measures of attention were not different between RTH and unaffected relatives. Thus, in this kindred, RTH is associated with specific impairments in language decoding, but not primary attention deficit.