Abstract
Familial resistance to thyroid hormone is characterized by elevated thyroid hormones and non-suppressed TSH in euthyroid individuals. We present a unique occurrence of an infant with neonatal hyperthyroidism and resistance to thyroid hormone in a family with 3 generations of resistance to thyroid hormone. He was born at 35 weeks gestation to a consanguinous relationship (first cousins), birth weight 1480 g, length 46 cm. He had fetal and neonatal (200 beats/min) tachycardia and exopthalmos. At 3 weeks of age the following was obtained: T4 50.7 ug/dL, T3RIA 1349 ng/dL, T3RU 45.9%, rT3 618 ng/dL, TSH 389 uIU/mL, free T4 25.7 ng/dL, free T3 5385 pg/dL, TBG 2.3 ng/dL, TBII 18 (n1<14), TSIg 167% (n1<130%), 4h 123I uptake 87% and 24h 50%, moderately enlarged gland on scan, negative thyroid antibodies. TRH increased the TSH from 317 to 413 at 30 min. Patient's father, paternal aunt and paternal grandmother have well documented resistance to thyroid hormone. One month postpartum the mother had the following: T4 19 ug/dL, T3RIA 298 ng/ dL, free T4 4.5 ng/dL, free T3 698 pg/dL, TSH 1.0 uIU/mL, TBG 2.8 ng/dL (n1 1.6-3.6), negative TBII and TSIg, nl TSH response to TRH. Maternal grandfather also had elevated thyroid indices (T4 15.2 ug/dL, T3RIA 229 ng/dL), nonsuppressed TSH 2.2 uIU/mL, and normal TRH stimulated TSH. We postulate that this neonate is a homozygote for this gene defect. We hypothesize that this infant's hyperthyroxinemia resulting in thyrotoxicosis may be expressed due to genetic inherited factors from both parents.
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Malkani, A., Escoto, D., Root, A. et al. FAMILIAL RESISTANCE TO THYROID HORMONE PRESENTING AS NEONATAL THYROTOXICOSIS. Pediatr Res 21 (Suppl 4), 250 (1987). https://doi.org/10.1203/00006450-198704010-00495
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DOI: https://doi.org/10.1203/00006450-198704010-00495