The liver and circulating thyroid hormones.

The liver plays a major role in modifying the total circulating hormone concentrations of thyroxine and triiodothyronine by secretion and degradation of carrier proteins. It also is a major site of peripheral conversion, degradation, and excretion of thyroid hormones. We review the liver's role in thyroid hormone physiology and summarize the changes in circulating thyroid hormone concentrations in various liver diseases.