RESISTANCE TO THYROID HORMONE DUE TO A NOVEL THR- MUTATION IN A PATIENT WITH THYROID AGENESIS

Refetoff Syndrome is a rare disorder characterized by resistance to thyroid hormone (RTH). The coexistence of RTH and thyroid dysgenesis is a rare event. Up to now, only four cases of ectopic gland and RTH have been reported. We report the first case with both thyroid agenesis and RTH. The patient referred to our center because of a high level of thyroid-stimulating hormone (TSH) at newborn screening. Laboratory analysis and thyroid ultrasound confirmed diagnosis of congenital hypothyroidism caused by athyreosis. Therefore, treatment with levothyroxine was started. During the follow-up, despite persistent mild elevation of serum free thyroxine concentrations, TSH level remained at the upper limit of the reference range. Direct sequencing of the thyroid hormone receptor B (THR-B) gene identified intronic variant (c.1144+9G>A). RTH may occur in presence of thyroid dysgenesis and this association suggests a hypothetic role of the THR-p in thyroid organogenesis.