endocrine and metabolic disorders
Hyperthyroidism
Pathophysiology of Hyperthyroidism
In hyperthyroidism, serum T3 usually increases more than does T4, probably because of increased secretion of T3 as well as conversion of T4 to T3 in peripheral tissues. In some patients, only T3 is elevated (T3 toxicosis). T3 toxicosis may occur in any of the common disorders that cause hyperthyroidism, including Graves disease, multinodular goiter, and the autonomously functioning solitary thyroid nodule. If T3 toxicosis is untreated, the patient usually also develops laboratory abnormalities typical of hyperthyroidism (ie, elevated T4 and iodine-123 uptake). The various forms of thyroiditis commonly have a hyperthyroid phase followed by a hypothyroid phase. 