Familial dysalbuminemic hyperthyroxinemia

Familial dysalbuminemic hyperthyroxinemia, or FDH, is a rare autosomal dominant genetic condition associated with mutations in the human serum albumin gene, and it is a common cause of euthyroid hyperthyroxinemia. The mutations produce an abnormal albumin that binds thyroid hormones with higher affinity than normal albumin, so affected people have high levels of thyroxine (T4) while their thyroid stimulating hormone (TSH) stays normal. Because of this pattern the condition is often mistaken for resistance to thyroid hormone syndromes or for hyperthyroidism.