Liver damage caused by PBC can lead to changes in the expression of the enzyme D3 that controls the activity of thyroid hormones (Gilgenkrantz and Collin de l'Hortet, 2018), which can lead to a decrease in the accumulation of active thyroid hormones (Elbers et al., 2016), can trigger hypothalamic–pituitary–thyroid regulation disorders, and can increase TSH, leading to hypothyroidism. This evidence concerns the gene TG and hypothyroidism.