DUOX2

Congenital hypothyroidism

Researchers have identified several DUOX2 gene mutations that cause congenital hypothyroidism, a condition characterized by a reduction of thyroid hormone levels that is present from birth. Most of these mutations result in an abnormally small version of the dual oxidase 2 enzyme. The remaining mutations change one of the building blocks (amino acids) used to make the enzyme, which probably alters the enzyme's structure. All DUOX2 gene mutations limit the enzyme's ability to generate hydrogen peroxide. Without sufficient hydrogen peroxide, thyroid hormone production is disrupted. In some cases, the thyroid gland is enlarged (goiter) in an attempt to compensate for reduced thyroid hormone production. Because cases caused by mutations in the DUOX2 gene are due to a disruption of thyroid hormone synthesis, they are classified as thyroid dyshormonogenesis.

The reduction in thyroid hormone production is affected by the number of DUOX2 genes with a mutation. Each cell in the body has two copies of the DUOX2 gene. If both copies of the gene have a mutation, cells in the thyroid gland generate very little hydrogen peroxide. As a result, thyroid hormone levels are extremely low, causing severe congenital hypothyroidism. If only one copy of the DUOX2 gene is mutated, some hydrogen peroxide is produced. As a result, thyroid hormone levels are slightly reduced, causing mild congenital hypothyroidism. Sometimes, mild congenital hypothyroidism is temporary (transient), and thyroid hormone levels that are low during infancy increase with age.