Without a functioning thyroid, the body would not be able to break down proteins and it would not be able to process carbohydrates and vitamins. For this reason, problems with this gland can lead to uncontrollable weight gain. For many people, these irregularities can be controlled through medications, as well as a modification of their diet.
However, there is one other controlling factor. The gland cannot produce hormones on its own. It needs the assistance of the pituitary gland, which creates thyroid stimulating hormone (TSH). As a result, a nonfunctional pituitary gland will eventually lead to thyroid-gland-related issues. TSH will either trigger the production of thyroxine or triiodothyronine. If TSH is not present at the right levels, too much or too little of either hormone will be made.