Animal models of nonthyroidal disease

The LAST TWO decades have witnessed an explosion in our knowledge of the physiology and pathophysiology of the thyroid hormone system. This is due, in part, to the application of radioimmunoassay methodology for the measurement of the thyroid hormones, L-thyroxine (T₄) and 1-3,5,3′-triiodothyronine (T₃). Numerous investigations have defined the changes in thyroid hormone production, binding to serum binding proteins, serum concentrations, metabolism, regulation by hypothalamic-pituitary axis, and actions which occur in hyperthyroidism and hypothyroidism. In parallel with these developments, clinical investigators have quickly appreciated the fact that the presence of diseases not related to the thyroid often has a significant impact on various measurements of thyroid function. Indeed, one of the most common reasons for consulting the clinical endocrinologist in hospitalized patients is to help interpret abnormalities in tests of thyroid function in patients who have a nonthyroidal disease.