The thyroid is a small, butterfly-shaped gland in the front of your neck that wraps around your windpipe (trachea). The two halves of the thyroid gland are connected in the middle by a thin layer of tissue known as the isthmus. The thyroid gland uses iodine (mostly absorbed from food) to produce hormones that control how your body uses energy. Your thyroid gland function affects nearly every organ in your body.
The pituitary gland and hypothalamus, an area at the base of the brain, control the rate at which the thyroid produces and releases these hormones. The main function of the thyroid gland is to release a hormone called thyroxine or T4, which is converted into a hormone called T3. Both hormones circulate in the bloodstream and help regulate your metabolism. The amount of T4 produced by the thyroid gland is determined by a hormone produced by the pituitary gland called TSH or thyroid-stimulating hormone. Depending on T4 levels in the body, the pituitary gland produces either more or less TSH in order to prompt the thyroid to produce the appropriate amount of T4.
Thyroid disease occurs when the thyroid fails to function properly, either by releasing too much T4 hormone or by not releasing enough. Your thyroid may also develop a lump or nodule. There are three main thyroid disorders:
Hypothyroidism occurs when the thyroid gland does not produce enough T4 hormone. Underactive thyroid may occur because the pituitary gland, the hypothalamus, or the thyroid itself is not working properly. Nearly five percent of the population has an underactive thyroid. More women than men suffer from the condition. Symptoms of an underactive thyroid include:
Hyperthyroidism occurs when the thyroid gland produces more thyroid hormone than the body needs. Overactive thyroid may occur because the hypothalamus, the pituitary gland, or the thyroid itself is not working properly. Overactive thyroid is not very common. It only affects a little over one percent of the U.S. population. Just like underactive thyroid, more women than men suffer from the condition.
Symptoms of an overactive thyroid include:
Older patients may experience arrhythmias (irregular heart rhythms), heart failure, and mental confusion (delirium). Left untreated, patients can suffer from a "thyroid storm" in which high blood pressure, heart failure, and fever can lead to a critical situation requiring urgent medical care.
