The
thyroid 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 in men) and at approximately the same level as the
cricoid cartilage. The thyroid controls how quickly the body burns
energy, makes
proteins, and how sensitive the body should be to other
hormones.
The thyroid participates in these processes by producing thyroid hormones, principally
thyroxine (T4) and
triiodothyronine (T3). These hormones regulate the rate of
metabolism and affect the growth and rate of function of many other systems in the body.
Iodine is an essential component of both T3 and T4. The thyroid also produces the hormone
calcitonin, which plays a role in
calcium homeostasis.
The thyroid is controlled by the
hypothalamus and
pituitary. The gland gets its name from the Greek word for "door", after the shape of the related thyroid cartilage.
Hyperthyroidism (overactive thyroid) and
hypothyroidism (underactive thyroid) are the most common problems of the thyroid gland