thyroid diverticulum

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thy·roid di·ver·tic·u·lum

, thyroglossal diverticulum
the endodermal bud from the floor of the embryonic pharynx; the primordium of the parenchyma of the thyroid gland.


1. resembling a shield.
2. the thyroid gland (see below) secreting thyroid hormones (see below).
3. a pharmaceutical preparation of cleaned, dried, powdered thyroid gland, obtained from those domesticated animals used for food by humans.

accessory thyroid
an additional thyroid located anywhere from the larynx to diaphragm, e.g. intrapericordial aorta; may be sufficient to supply the patient's need of thyroid hormone. Most common in dogs.
thyroid C cell
see c cell.
thyroid cartilage
the shield-shaped cartilage of the larynx.
thyroid diverticulum
primordium of the thyroid gland; appears as an outgrowth of the foregut between the first two pharyngeal pouches. This tube of epithelial cells grows ventrally into mesenchyme; the tube becomes the thyroglossal duct, the tip divides into two lobes, the thyroid glands.
thyroid dysfunction
ectopic thyroid
migration of thyroid diverticulum tissue to aberrant sites occurs, e.g. thyroid tissue in the thymus. These cause no apparent abnormality.
thyroid extract
a pharmaceutical substance derived from thyroid glands, used in the treatment of hypothyroidism. See thyroid (3) (above).
thyroid function tests
used to assess the functional capacity of the thyroid glands; most commonly employed in dogs and cats. Include plasma T4, plasma T3, free T4 radioiodine uptake, and TSH response tests.
thyroid gland
the largest of the endocrine glands, situated in the neck caudal to the larynx. It produces hormones (see below) that are vital in maintaining normal growth and metabolism. It also serves as a storehouse for iodine.
Enlarge picture
Microscopic appearance of the thyroid gland. By permission from Guyton R, Hall JE, Textbook of Medical Physiology, Saunders, 2000
thyroid hormones
iodothyronines secreted by the thyroid gland, principally thyroxine (tetraiodothyronine, T4) and tri-iodothyronine (T3); derived from iodination of tyrosyl residues in thyroglobulin. The pharmaceutical names for T4 and T3 are levothyroxine and liothyronine, respectively. Regulate basal metabolic rate.
thyroid parafollicular cell
see c cell.
thyroid radioiodine uptake
used as a thyroid function test but superseded these days by estimates of T4 (thyroxine).
thyroid-stimulating hormone (TSH)
thyroid tumor
mostly follicular adenomas in old-aged dogs, cats and horses; papillary adenomas are rare.