| hormone, thyroid stimulating | A hormone produced by the pituitary gland (at the base of the brain) that promotes the growth of the thyroid gland (in the neck) and stimulates it to produce its thyroid hormones. Normally, the rate of thyroid hormone production is controlled by the pituitary. When there are insufficient thyroid hormones in the body for normal functioning of the cells, the pituitary releases tsh. Tsh in turn stimulates the thyroid gland to produce more thyroid hormones. In contrast, when there is excessive amount of thyroid hormones, the pituitary gland stops producing tsh. The tsh level then falls and thyroid hormone production is reduced. This mechanism maintains a relatively constant level of thyroid hormones circulating in the blood. This phenomenon is analogous to a thermostat used for temperature regulation in a room: when the temperature rises, the thermostat shuts the heater off and the room temperature falls back to normal. High levels of thyroid hormones cause the tsh level to fall, resulting in no further stimulation of the thyroid gland. In hyperthyroidism, there are continuously elevated levels of the thyroid hormones. Tsh is also known as thyrotropin. (12 Dec 1998) |
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| horns of thyroid cartilage | See: inferior horn of thyroid cartilage, superior horn of thyroid cartilage. (05 Mar 2000) |
| hot thyroid nodule | <radiology> Almost always hyperfunctioning adenoma, vast majority benign, up to 50% are autonomous see also: thyroid carcinoma, cold thyroid nodule (12 Dec 1998) |
| pyramidal lobe of thyroid gland | <anatomy> An inconstant narrow lobe of the thyroid gland that arises from the upper border of the isthmus and extends upward, sometimes as far as the hyoid bone; it marks the point of continuity with the thyroglossal duct. Synonym: lobus pyramidalis glandulae thyroideae, Lallouette's pyramid, Morgagni's appendix, pyramid of thyroid. (05 Mar 2000) |
| pyramid of thyroid | <anatomy> An inconstant narrow lobe of the thyroid gland that arises from the upper border of the isthmus and extends upward, sometimes as far as the hyoid bone; it marks the point of continuity with the thyroglossal duct. Synonym: lobus pyramidalis glandulae thyroideae, Lallouette's pyramid, Morgagni's appendix, pyramid of thyroid. (05 Mar 2000) |
| sheath of thyroid gland | Covering of the thyroid gland external to its capsule formed by a splitting of the pretracheal layer of deep cervical fascia at the gland's posterior border; the anterior lamina covers the gland anterolaterally, attaching to the arch of the cricoid cartilage superior to the isthmus of the gland (causing it to move with the trachea during elevation/depression of the larynx); the posterior lamina passes posterior to the oesophagus to blend with the buccopharyngeal fascia; inferiorly, the sheath extends along the inferior thyroid veins to open into the superior mediastinum (hence, expansion of the thyroid, as by goiter, can take this direction). (05 Mar 2000) |
| stroma of thyroid gland | The connective tissue that supports the lobules and follicles of the thyroid gland. Synonym: stroma glandulae thyroideae. (05 Mar 2000) |
| suspensory ligament of thyroid gland | One of several fibrous bands which pass from the sheath of the thyroid gland to the thyroid and cricoid cartilages. (05 Mar 2000) |
| discordant thyroid nodule | <radiology> Hot on Tc-99m pertechnetate, cold on I-123 or I-131, indicates trapping, but no organification, same work-up as cold nodule (12 Dec 1998) |
| immunoglobulins, thyroid-stimulating | Autoantibodies that bind to the thyroid-stimulating hormone (tsh) receptor (receptors, thyrotropin) on thyroid epithelial cells. The autoantibodies mimic tsh causing an unregulated production of thyroid hormones characteristic of graves' disease. (12 Dec 1998) |
| inferior horn of thyroid cartilage | One of the pair of downward prolongations at the back of the thyroid cartilage; it articulates on each side with the cricoid cartilage. Synonym: cornu inferius cartilaginis thyroideae. (05 Mar 2000) |
| inferior thyroid artery | <anatomy, artery> Origin, terminal branch of thyrocervical trunk (with ascending cervical artery); branches, inferior laryngeal, and muscular, oesophageal, and tracheal. Synonym: arteria thyroidea inferior. (05 Mar 2000) |
| inferior thyroid notch | A shallow notch in the middle of the lower border of the thyroid cartilage. Synonym: incisura thyroidea inferior. (05 Mar 2000) |
| inferior thyroid plexus | An autonomic plexus on the artery of this name, derived from the subclavian plexus. Synonym: plexus thyroideus inferior. (05 Mar 2000) |
| inferior thyroid tubercle | A slight lateral projection from the lower margin of the lamina of the thyroid cartilage on either side, at the inferior end of the oblique line. Synonym: tuberculum thyroideum inferius. (05 Mar 2000) |