Resistance to thyroid hormones (RTH): study of a family
Jacinta Santos1, Isabel Paiva1, Carla Baptista1, P Beck-Peccoz2 & Manuela Carvalheiro1
Resistance to thyroid hormones (RHT) is a rare syndrome, with autosomic dominant transmission, due to mutations in thyroid hormones beta-receptor gene. Clinical presentation is variable for the same mutation. This hypothesis must be considered in presence of high levels of thyroid hormones and TSH not suppressed.
The evaluation of a 15-year-old female patient, in 1990, harbouring a thyroid nodule, secondary amenorrhea and visual and auditory impairment showed slightly elevated thyroid hormone levels but normal TSH. She started levothyroxine treatment and resumed menses. She was lost to follow up. Three years later, returned to consultation with a multinodular goiter, high levels of thyroid hormones and high TSH, in spite of levothyroxine treatment. After TRH stimulation and pituitary MRI, resistance to thyroid hormones was diagnosed. Treatment was tried with tri-iodotironine and TRIAC, with slight reduction of TSH. In 2004, a new radiologic evaluation suggested a pituitary microadenoma, fully described with 10 mm in 2006. No other hormonal disorders were detected. A not yet described mutation in exon 9 (G344R) was identified by Professor Beck-Peccoz team. We studied patients family mother, two brothers and two sisters (one of them is a non-identical twin sister of our patient). Father was already deceased. We found abnormalities in thyroid hormone levels in both brothers, who also have the mutation. MRI of one of them suggests a pituitary microadenoma.
Conclusions: We describe a family with Resistance to Thyroid Hormones Syndrome due to a new mutation in thyroid hormone receptor beta G344R. Until now, a pituitary microadenoma was diagnosed in two of the affected patients, which is a rare pathological situation that can occur in the natural history of RTH.