ABSTRACT
A 23-year-old man and his grandmother with hyperthyroxinemia and hypercortisolemia were heterozygous for an ALB mutation (p. Arg218Pro), known to cause familial dysalbuminemic hyperthyroxinemia (FDH). However, serum-free cortisol levels in these individuals were normal and total cortisol concentrations fell markedly after depletion of albumin from their serum. We conclude that binding of steroid as well as iodothyronines to mutant albumin causes raised circulating cortisol as well as thyroid hormones in euthyroid euadrenal individuals with R218P FDH, with potential for misdiagnosis, unnecessary investigation, and inappropriate treatment.
Subject(s)
Hydrocortisone/blood , Hyperthyroxinemia, Familial Dysalbuminemic/complications , Hyperthyroxinemia/complications , Mutation , Serum Albumin, Human/genetics , Albumins/chemistry , Genotype , Heterozygote , Humans , Immunoassay , Male , Military Personnel , Protein Binding , Serum Albumin/genetics , Steroids/chemistry , Thyronines/blood , Thyroxine/blood , Young AdultABSTRACT
We herein report the case of a Japanese woman with familial dysalbuminemic hyperthyroxinemia (FDH) who was initially diagnosed with Graves' disease. Direct genomic sequencing revealed a guanine to cytosine transition in the second nucleotide of codon 218 in exon 7 of the albumin gene, which then caused a proline to arginine substitution. She was finally diagnosed with FDH, which did not require treatment. FDH is - superficially - an uncommon cause of syndrome of inappropriate secretion of thyrotropin (SITSH) in Japan. A misdiagnosis of pseudo-hyperthyroidism will lead to inappropriate treatment. Thus, physicians should strongly note the possibility of FDH as a differential diagnosis of SITSH.
Subject(s)
Antithyroid Agents/therapeutic use , Hyperthyroxinemia, Familial Dysalbuminemic/diagnosis , Hyperthyroxinemia, Familial Dysalbuminemic/drug therapy , Methimazole/therapeutic use , Adult , Codon , Diagnosis, Differential , Female , Graves Disease/diagnosis , Humans , Hyperpituitarism/etiology , Hyperthyroxinemia, Familial Dysalbuminemic/complications , Hyperthyroxinemia, Familial Dysalbuminemic/genetics , Mutation , Serum Albumin/genetics , Thyroid Gland/diagnostic imaging , Thyrotropin/metabolism , UltrasonographyABSTRACT
Here we report the case of a young girl who had vague signs and symptoms potentially attributable to hyperthyroidism and was found to have autoimmune thyroiditis and hyperthyroxinemia. The elevated serum free thyroxine levels were persistent when measured by both standard assays and equilibrium dialysis/high-pressure liquid chromatography-tandem mass spectrometry. The clinical symptoms, with discordant thyroid test results, created a diagnostic dilemma that led initially to unnecessary additional evaluations. She was ultimately found to have familial dysalbuminemic hyperthyroxinemia (FDH) and required no therapy. This case highlights the inherent difficulties in evaluating children, who typically have vague signs and symptoms of thyroid dysfunction, when, in addition, they have an unrelated acquired (autoimmune) as well as a genetic (FDH) defect. The benefit of including testing for immediate members of the family is emphasized.
