title: Thyroid function tests in patients with familial dysalbuminaemic hyperthyroxinaemia (FDH).
abstract: Two patients with familial dysalbuminaemic hyperthyroxinaemia (FDH) are described in whom the albumin variant resulted in raised total T4 levels, and artefactually raised free T4 using a 'single-step' technique employing an analogue of T4 as tracer. The first patient was clinically euthyroid and presented with relapse of schizophrenia and abnormal thyroid function tests (total T4 336 nmol/L, total T3 4.2 nmol/L, TSH 1.8 mU/L, free T4 73 pmol/L). These results led to diagnostic confusion and the patient was treated with a short course of anti-thyroid drugs. The second patient had signs and symptoms of thyrotoxicosis at her first visit but was clinically euthyroid 5 months later when she was 10 weeks pregnant. Thyroid function tests were total T4 259 nmol/L, total T3 3.6 nmol/L, TSH 3.8 mU/L, free T4 46 pmol/L. Further studies showed both patients to be biochemically euthyroid. A variant albumin was confirmed in both patients by a screening test for FDH and by reverse-flow electrophoresis. Family studies on 10 relatives of the first patient identified eight with FDH. A simple screening procedure for the indentification of FDH is described and the use of laboratory tests in suspected cases is discussed.
mesh_terms: D000328:Adult; D005067:Euthyroid Sick Syndromes / Q000097:blood / Q000150:complications; D005260:Female; D006801:Humans; D006981:Hyperthyroxinemia / Q000175:diagnosis / Q000235:genetics* / Q000503:physiopathology; D010375:Pedigree; D012559:Schizophrenia / Q000097:blood / Q000150:complications; D012709:Serum Albumin / Q000235:genetics* / Q000378:metabolism; D013960:Thyroid Function Tests; D013974:Thyroxine / Q000097:blood* / Q000378:metabolism
chemical_list: D012709:Serum Albumin; D013974:Thyroxine