The Thyroid is one of the largest endocrine glands, its primary function is to secrete hormones. By means of these hormones, the thyroid controls the body's metabolism, creates proteins, and sensitizes the body to other hormones. The thyroid hormones are essential for nerve development, sexual development, and physical growth as well as for regulating the metabolic rate, body heat, and energy level.
A variety of things can go wrong with the thyroid. Most of the time, thyroid conditions end up in one of two categories: hypothyroidism and hyperthyroidism.
Hypothyroidism occurs when your thyroid isn't producing enough thyroid hormone to keep up with what your body needs. This can be due to a sluggish thyroid gland (for a variety of reasons), a lack of enough thyroid-stimulating hormone by your pituitary gland, a lack of adequate nutrients the thyroid needs to function, a problem with receptor sites throughout the body, or an autoimmune disease like Hashimoto's Disease. There also may be a problem with thyroid hormone receptor sites throughout the body.
Hyperthyroidism occurs when your thyroid produces too much thyroid hormone. Simply put, the body has a regulator (thyroid) for metabolism and body maintenance and the dial gets turned up too high. This is a very serious problem. In hypothyroidism, where the thyroid is underfunctioning, you may feel miserable, but you can still live with it for a long time. Hyperthyroidism, on the other hand, is a great deal more serious.