Endocrine Abstracts

Introduction: The syndrome of resistance to thyroid hormone is a rare inherited disorder characterized by elevated circulating thyroid hormones, failure to suppress pituitary thyroid stimulating hormone (TSH) and variable tissue target hyposensitivity to thyroid hormone action. We reported the case of a RTH syndrome with a novel mutation.

Case report: A 15-year-old girl was investigated for visual hallucinations and behavior disorders. Her medical history was unremarkable except for a learning disability and a hyperactivity disorder in childhood. There was no family history of thyroid diseases and she was not taking any regular medication. She was found to have abnormal thyroid function tests with increased plasma free T₃, free T₄ of 2.51 ng/dl (reference range: 0.71–1.85 ng/dl) with non-suppressed TSH of 7.7 μUI/ml (referance range: 0.12–3.4 μUI/ml). On examination, weight was 48 kg, height was 141 cm, blood pressure was normal and pulse rate was 92 beats/min. She had clinical symptoms of thyroid hormone excess: moist skin, insomnia and agitation. She had no goiter or dysthyroid eye disease. Repeated thyroid function tests confirmed previous findings. Thyroid antibodies (anti-peroxydase and anti-TSH receptor) were negative. The level of TSH α-subunit was normal 0.54 μUI/ml (range: 0.05–0.9) and the ratio TSH α-subunit/TSH was less than 1. TSH-secreting tumor was ruled out by normal pituitary magnetic resonance imaging (MRI). Genetic analysis yielded a novel mutation in the THRβ gene, c.1369 G>A in exon 10, due to a base pair substitution of glutamic acid by lysine in position 457.

Discussion: We reported a novel mutation in the THRβ gene that has not been previously described and discussed the clinical presentation of the thyroid hormone resistance syndrome according to the different mutations.