What is the thyroid?
The thyroid is an H-shaped gland that sits in the lower part of the neck, in front of and to the sides of the trachea ('windpipe'). It has 2 lobes and a connecting isthmus. It has a rich blood supply. The hormone produced by the thyroid gland enters the bloodstream directly.
The parathyroid glands are located behind the thyroid gland. They are responsible for controlling the level of calcium in the body.
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The thyroid gland sits in the lower neck in front of and to the sides of the windpipe (trachea). The gland is made up of 2 lobes joined in middle by the isthmus. |
Side view showing thyroid lifted forward revealing the parathyroid glands and the arterial supply. (ITA = inferior thyroid artery, STA = superior thyroid artery) |
The nerves that supply the larynx ('voicebox') - the laryngeal nerves - can also be found behind the thyroid gland and in the groove between the gullet and the windpipe. The recurrent laryngeal nerve is shown in the picture above (see also the section on surgery).
The thyroid gland uses iodine to produce thyroid hormone (thyroxine) - a process under the control of the brain (from the pituitary gland) via another hormone called thyroid stimulating hormone (TSH). The levels of this are in turn controlled by the blood levels of thyroxine. Thyroid hormone regulates a number of body functions including:
