The thyroid is a butterfly shaped endocrine gland, below the larynx in your throat, that plays a major role in the metabolism of the human body. Its effects are felt by every single cell within your body.
Sadly, issues with the thyroid producing too many hormones, or too little, are rampant in industrialized peoples. These metabolic diseases are not easy fixes, as metabolism is a system-wide function. Thus, the cause and effects are spread throughout the system as well.