Carcinoma of the thyroid gland.

By location, the thyroid is protected from those extrinsic carcinogenic stimuli which affect surface epithelium. Thyroid tissue may enter into a hyperplastic phase, however, as a result of infection, intoxication, pregnancy, deficiency states (vitamin and mineral), and emotional stress. From a functional standpoint the thyroid gland is in a constant state of flux, in response to physiologic and pathologic stimuli. Continued overactivity results in hyperplasia, which may involve the gland as a whole, as in pregnancy, or may be limited to a single or multiple foci, adenomata. Residua of these hyperplastic centers are carried throughout the life of the individual and are potential sources of neoplastic metamorphosis. In fact, 90 per cent of all thyroid carcinomata have been said to arise in pre-existing adenomata (Portmann, 1). To function normally, the thyroid requires a minute but constant supply of iodine. In regions where the basic iodine intake is deficient, goiter is more common, and “when goiter is en...