Familial dysalbuminemic hyperthyroxinemia (FDH): inadequacy of the "analog" methods for assaying free-T4 levels.
Free-T4 levels were determined in familial dysalbuminemic hyperthyroxinemia (FDH) subjects. In agreement with their euthyroid status free-T4 levels were within the normal range when tested by equilibrium dialysis and by the FT4 Immophase method (Corning Medical). However, when using the recently introduced "analog" methods, either Amerlex FT4 or Becton-Dickinson FT4, Free-T4 values were markedly higher than the control values. This discrepancy is probably due to artifactual binding of the labeled analog to the fraction of albumin exhibiting an excessive affinity for T4.
D006801:Humans; D008722:Methods; D011485:Protein Binding; D011933:Reagent Kits, Diagnostic; D012709:Serum Albumin / Q000378:metabolism*; D013974:Thyroxine / Q000097:blood*
D011933:Reagent Kits, Diagnostic; D012709:Serum Albumin; D013974:Thyroxine