Endocrine Abstracts

Resistance to thyroid hormone (RTH) is usually due to heterozygous mutations in THRB gene with rare cases being homozygous for receptor defects. We describe an RTH case due to a homozygous TRβ mutation (R243Q).The Proband (male, 8.4 years), was born at term with low birth weight (1.9 kg) to consanguineous parents. He has a prominent nasal bridge, goitre, low body weight (10th centile), recurrent tonsillitis, hyperactivity and has mild hearing impair...

The differential diagnosis of raised circulating thyroid hormones with normal TSH includes familial dysalbuminaemic hyperthyroxinaemia (FDH), a benign, inherited disorder caused by a variant albumin with increased affinity for thyroxine (T4) or triiodothyronine (T3). Three different albumin gene mutations, generating mutant proteins with increased affinity for either T4 (R218H,R218P) or T3 (L66P) have been commonly described. Typically, serum total T4 is raised and free T4 mea...

Resistance to Thyroid Hormone alpha (RTHα) is characterised by tissue-selective hypothyroidism with near-normal thyroid function tests, and is due to thyroid receptor α gene mutations. We sought to correlate the clinical characteristics and response to thyroxine treatment of two RTHα patients with the properties of their defective TRα proteins.Clinical, biochemical and physiological parameters were assessed in each patient at baseline...

Introduction: Thyroid hormones act via receptors encoded by different genes (THRA and THRB) generating receptor subtypes (TRα1, TRβ1, TRβ2) with differing, tissue-specific expression. Resistance to Thyroid Hormone due to THRB defects is well recognised, but no THRA mutations have yet been reported. We describe the first case of human TRα-mediated thyroid hormone resistance due to a dominant negative THRA mutation.Results: A 6-year-old...

Introduction: Thyroid hormones act via receptors encoded by different genes (THRA and THRB) generating receptor subtypes (TRα1, TRβ1, TRβ2) with differing, tissue-specific expression. Resistance to thyroid hormone due to THRB defects is well recognised, but no THRA mutations have yet been reported. We describe the first case of human TRα-mediated thyroid hormone resistance due to a dominant negative THRA mutation.<p cl...

Selenocysteine insertion sequence-binding protein 2 (SECISBP2) mediates translational incorporation of selenocysteine into 25 known human selenoproteins, including iodothyronine deiodinases. Two unrelated male subjects, aged 36 years (P1) and 3.6 years (P2), exhibited markedly elevated free thyroxine (fT4), normal/low free triiodothyronine (fT3), but normal thyrotropin (TSH) levels, indicating reduced T4 to T3 conversion:<table b...

Objectives: THRA mutations cause Resistance to Thyroid Hormone α (RTHα), an underdiagnosed disorder with hypothyroid features but near-normal thyroid function tests (TFTs). We developed a pathway, combining molecular analyses, new biomarkers and physiological measurements, to better diagnose and treat this disorder.Methods: Structural and functional analyses of THRA variants, discovered by next generation sequencing in specifi...