Figure 2: Changes in deiodinase type 1 and deiodinase type 3 in chronic liver injury drives intrahepatic hypothyroidism.

In the normal liver, DIO1 activity, an intrahepatic enzyme, drives the conversion of T4 to active T3. In chronic liver injury, a decrease in DIO1 activity coupled with an increase in DIO3 activity leads to increased conversion of T4 to inactive reverse T3, subsequently leading to accumulation of lipotoxic species, cyclic liver injury and local intrahepatic hypothyroidism. Used with permission from ©Mount Sinai Health System.

DIO1 = deiodinase type 1; DIO3 = deiodinase type 3; rT3 = reverse triiodothyronine; T3 = triiodothyronine; T4 = thyroxine; TRH = thyroid-releasing hormone; TSH = thyroid-stimulating hormone.