The thyroid gland is one of the largest endocrine glands in the body. This gland is found in the neck, inferior to (below) the thyroid cartilage (also known as the Adam's apple) and at approximately the same level as the cricoid cartilage. The thyroid controls how quickly the body uses energy, makes proteins, and controls how sensitive the body should be to other hormones.
The thyroid takes part in these processes by producing thyroid hormones, principally thyroxine (T4) and triiodothyronine (T3). Thyroid tissues trap iodine circulating in the blood and use it to produce thyroxine and triiodothyronine. These hormones regulate the rate of metabolism and affect the growth and rate of function of many other systems in the body. Iodine and tyrosine are used to form both T3 and T4. The thyroid also produces the hormone calcitonin, which plays a role in calcium homeostasis.
The thyroid gland is regulated by the hypothalamus and pituitary. The gland gets its name from the Greek word for "shield", after the shape of the related thyroid cartilage. Hyperthyroidism (overactive thyroid) and hypothyroidism (underactive thyroid) are the most common problems of the thyroid gland.
Thyroid Gland Video