SUMMARY Resistance to
thyroid hormone (RTH) coexisting with
ectopic thyroid is rare. Here we
report a case of RTH with
ectopic thyroid. A ten-year-old
girl had been misdiagnosed as
congenital hypothyroidism and treated with levothyroxine since she was born. Ten-year follow-up showed that the elevated
thyrotropin was never suppressed by levothyroxine and no signs indicating
hyperthyroidism or
hypothyroidism despite elevated FT3 and FT4 levels. Therefore the
girl developed no defects in physical and cognitive development.
Pituitary adenoma was excluded by
magnetic resonance imaging.
Ultrasonography did not find the
thyroid gland in the normal place, while the
thyroid scan found a large
lingual thyroid gland. The
octreotide inhibition test showed a reduction in
thyrotropin by 41.98%. No
mutation was detected in the
thyroid hormone receptor (THR) β, THRα,
thyrotropin receptor (TSHR), and GNAS1
genes. To our
knowledge, it is an interesting RTH case coexisting with
lingual thyroid.