John Eckhart Jr. age 14, of Phoenix, Ariz., for his question:
WHERE IS THE THYROID AND WHAT DOES IT DO?
The thyroid secretes several hormones needed in certain body processes, such as growth and the conversion of food into energy. This important gland is located in the neck just below the Adam's apple. It is sometimes called the butterfly gland because it is shaped much like a butterfly with its wings open or an hourglass turned on its side.
Made of solid tissue, the thyroid weighs only about one ounce. It is nearly three inches wide and about two inches high at the tips of the wings. The right wing is slightly larger than the left.
The upper points of the wings are attached to the sides of the Adam's apple (thyroid cartilage). The gland hangs down from these, around and in front of the windpipe (trachea), so that it moves with every swallow.
One of the richest supplies of blood in the body is found in the thyroid. Four to five quarts are estimated to flow through it each hour. The red blood cells move from nearby neck arteries to the spaces between the follicles and out through the neck veins, continually carrying with them a new supply of thyroid hormones.
The gland is also well supplied with lymphatics, much like veins of watery fluid. These help dissolve and carry wastes and fluids from the tissues to the blood system.
The primary secretion of the thyroid follicles is a hormone called thyroxine, which is produced in large quantities. This is an amino acid hormone containing iodine. Thyroxine affects or controls many body activities. It increases the rate at which foods are turned into energy and bodily proteins are built. It influences the growth of children. It stimulates thought processes and also the action of numerous other endocrine glands.
Underactivity of the thyroid occurs when the gland does not produce enough thyroid hormone to meet even the normal everyday needs of the body.
Overactivity of the thyroid gland can occur either when the thyroid overcompensates for a temporary need for extra thyroid hormone or when the thyroid gland, or the other hormones and body chemicals that stimulate or contribute to the production of thyroid hormone, do not function properly.
Whatever the reason, the result is an increased rate of metabolism that is, conversion of oxygen and food products into energy and body tissue. The effect is much the same as racing the motor of a car while it is standing still.
The patient becomes nervous, overactive and restless, and may have occasional uncontrollable shaking, fast heartbeat and high blood pressure. He or she may feel weak, lose weight despite a large appetite, feel hot and sweat too much, or have many other varied symptoms. Sometimes the eyeballs bulge out, a symptom called exopthalmos.
The thyroid gland enlarges during this overactivity. In some cases it grows so large that it bulges over the outside of the lower neck, or spreads inside the throat and chest or both. This condition is known as a goiter.