What Is the Thyroid?
The thyroid is a small, butterfly-shaped gland just below the Adam's apple. This gland plays a central role in controlling the body's energy metabolism by producing four thyroid hormones that are carried throughout the body via the bloodstream. The way in which these hormones work can be likened to an air conditioner and the thermostat that regulates it. When there are sufficient thyroid hormones in the blood, the gland stops making them. This is the negative feedback principle of the air conditioner, which cycles off when the air is cool enough. Conversely, the thyroid turns up production when the need arises (when the air gets too warm).
In league with the thyroid is the pituitary gland, which works like the thermostat in your home. The pituitary tells the thyroid when to start and when to stop by sending thyroid-stimulating hormone to the thyroid.
It has been estimated that there are 20 million Americans who have some form of thyroid disease, much of which is undiagnosed or misdiagnosed. Although women are much more susceptible - thyroid deficiency may be as much as ten times more common in women than in men - no one of any age, race, sex, or economic status is immune. Age is definitely a factor in thyroid decline, which becomes ever more likely as we grow older.
Inadequate levels of thyroid hormones (hypothyroidism) is the most common problem, but some people have too much (hyperthyroidism). Other problems include inflammation of the thyroid gland (thyroiditis), enlargement (goiter), or the development of one or more lumps (nodules).