Thyroid hormone metabolism. A comparative evaluation.

Knowledge of thyroid hormone and iodide metabolism is derived from a combination of in vivo and in vitro studies in a variety of mammalian species including cats, dogs, and humans. Each species provides a unique opportunity to investigate various aspects of normal or altered thyroid hormone physiology. Availability of sensitive and specific human TSH assays has allowed detailed studies of the human hypothalamic-pituitary-thyroid axis which have not been possible in cats and dogs to date. Similarities and differences of thyroid hormone metabolism in dogs, cats, and humans provide the basis for a better understanding of normal physiology as well as shedding light on the significance of changes induced by spontaneous or induced thyroidal and nonthyroidal disorders.