THYROID (Gr. θυροειδής, shield-shaped, from θυρεός, a large oblong shield, shaped like a door, θύρα, and εἶδος, form), in anatomy, a term applied (1) to the largest of the cartilages of the larynx (see Respiratory System), (2) to one of two arteries which lie near the thyroid cartilage and gland (see Arteries), and (3) to a vascular ductless gland, which rests on the larynx and upper part of the trachea (see Ductless Glands). The thyroid gland is used in medicine in two forms. Thyroideum sicrum is a light dull brown powder, prepared by drying the thyroid gland of a sheep. Its chief constituent is a proteid known as thyreoglobulin, the active principle of which contains 9.3% of iodine and 0.5% of phosphorus, and is known as iodothyrin or thyroiodin. The dried gland easily becomes damp and deteriorates. Liquor thyroidei is a pink turbid liquid made by macerating the fresh gland of a sheep with glycerin and phenol.
Thyroid gland administered to man increases the pulse rate, causes increased and enfeebled cardiac beat and leads to increased metabolism, consequently excess of urea, uric acid and phosphates are excreted in the urine; it therefore reduces the body weight. Glycosuria develops from the inability of the body to ingest glucose. Overdoses of thyroid cause rapid pulse, headache and vomiting, together with diarrhoea and pruritus, emaciation and weakness. These symptoms are known as thyroidism.
Thyroid gland was introduced for the treatment of patients suffering from goitre, myxoedema and cretinism, in which diseases it has been remarkably successful, cretins growing rapidly under the thyroid treatment and developing intelligence. It has also been used in dwarfism, excessive obesity, psoriasis and scleroderma. When used in obesity an excess of nitrogenous food should be taken to balance the destruction of proteid. In certain forms of insanity, melancholia and climacteric insanities it has given good results. Full doses of thyroid are valuable in the prevention and relief of eclampsia. It should not be given to patients suffering from exophthalmic goitre, for which an anti-thyroid serum (antithyreoidin of Moebius), which is the serum of thyroidectomized animals, has been introduced.
Rodagen is a white powder consisting of the dried milk of thyroidectomized goats, mixed with 50 % of milk sugar. In exophthalmic goitre this preparation causes a reduction of the swelling and of the pulse rate, and an increase of body weight.