title: A case of thyroid hormone resistance: a rare mutation.
abstract: Reduced sensitivity to thyroid hormones (RSTH) is a rare disease that affects about 3,000 individuals, belonging to about 1,000 families. It results from reduced intracellular action of thyroid hormones (TH) genetically determined and manifests as persistent hyperthyroxinemia with non-suppressed thyroid-stimulating hormone (TSH). We describe a 67-years old, Caucasian woman, with past history of subtotal thyroidectomy due to diffuse goiter, who presents with a recurrence of goiter. Although she is clinically euthyroid, laboratory evaluation shows persistent hyperthyroxinemia with non-suppressed TSH. Response to thyrotropin releasing hormone (TRH) test was normal and TSH concentrations were not suppressed during oral administration of suprafisiologic doses of levothyroxine (L-T4). Peripheral blood DNA was extracted from the patient and a mutation was found localized in cluster one, at codon 346 of the ligand binding domain of the THRB gene. The patient's son underwent thyroid function testing (TFT) and genetic study, both negative, suggesting a sporadic mutation. RSTH should be considered in all hyperthyroxinemic patients who are clinically euthyroid. Mutations interfering with three major steps required for TH action on target tissues have been, so far, identified (TR-β, TR-α, MCT8, SPB2). Each mutation is associated with a distinctive syndrome. Goal of management is to maintain a normal serum TSH level and a eumetabolic state and offer appropriate genetic counselling and prenatal diagnosis. Inappropriate treatment of eumetabolic patients results in hypothyroidism and need for TH replacement.
authors: Hospital de Santa Maria, Centro Hospitalar Lisboa Norte, Portugal.
authors: Ana Pires
authors: AP
authors: Gonçalves
authors: Hospital de Santa Maria, Centro Hospitalar Lisboa Norte, Portugal.
authors: José Maria
authors: JM
authors: Aragüés
authors: Hospital de Santa Maria, Centro Hospitalar Lisboa Norte, Portugal.
authors: Ema
authors: E
authors: Nobre
authors: Hospital de Santa Maria, Centro Hospitalar Lisboa Norte, Portugal.
authors: Ana Paula
authors: AP
authors: Barbosa
authors: Hospital de Santa Maria, Centro Hospitalar Lisboa Norte, Portugal.
authors: Mario
authors: M
authors: Mascarenhas
mesh_terms: D000368:Aged; D004247:DNA / Q000032:analysis; D005091:Exons; D005260:Female; D018776:Genes, erbA; D006042:Goiter / Q000235:genetics; D006801:Humans; D006981:Hyperthyroxinemia / Q000097:blood; D009154:Mutation; D016133:Polymerase Chain Reaction; D035583:Rare Diseases / Q000235:genetics*; D018025:Receptors, Thyrotropin-Releasing Hormone / Q000097:blood / Q000187:drug effects; D012008:Recurrence; D013960:Thyroid Function Tests; D018382:Thyroid Hormone Resistance Syndrome / Q000235:genetics*; D013972:Thyrotropin / Q000097:blood / Q000187:drug effects; D013974:Thyroxine / Q000494:pharmacology
chemical_list: D018025:Receptors, Thyrotropin-Releasing Hormone; D013972:Thyrotropin; D004247:DNA; D013974:Thyroxine