What is Hypothyroidism?

The thyroid gland is an important endocrine gland that controls the bodys metabolism. It is a small butterfly-shaped gland located in the front of the neck just below the Adams apple. The thyroid gland produces the hormones tetraiodothyronine (T4) and triiodothyronine (T3).

Together these hormones regulate how your cells use energy. The pathways by which cells use energy is called metabolism. Your bodys general metabolism determines blood pressure, heart rate, and weight.

Hypothyroidism is a condition where your thyroid gland does not make enough thyroid hormone. Low levels of thyroid hormone interfere with the bodys ability to perform normal metabolic functions such as efficient use of energy from food products, regulation of many chemical reactions in the body, and maintenance of healthy cells, bones and muscles, to name a few.

There is no known prevention for hypothyroidism, nor is there a cure. Once you have it, you have it for life.

The most common causes are surgical removal of your thyroid, autoimmune diseases, and radiation treatment.

This may be necessary to treat hyperthyroidism, or tumors of the thyroid gland. Hypothyroidism will occur when the entire gland is removed.

These diseases cause the production of antibodies that attack your thyroid gland. Autoimmune thyroiditis, which can appear suddenly or develop over several years, is more common in women. Hashimotos thyroiditis and atrophic thyroiditis are the most common types.

Radiation treatment for Hodgkin lymphoma and cancers of the head and neck can injure the thyroid gland. If this occurs, the gland cannot produce enough thyroid hormone to keep your metabolism running smoothly. Radioactive iodine (I-131) destroys the thyroid gland and can be used to treat people with Graves disease and thyroid cancer. Graves disease is an autoimmune disease that causes hyperthyroidism.

Some children are born without a thyroid gland or they may have one that doesnt function properly.

More here:
Hypothyroidism: Causes, Symptoms, & Treatment