The thyroid is a butterfly-shaped endocrine gland located in the neck. This gland is responsible for producing two key hormones: thyroxine (T4), and triiodothyronine (T3). These hormones help regulate the metabolism and influence virtually every organ system in the body. These key thyroid hormones essentially tell organs how fast or slow they should work. Thyroid hormones also regulate the body’s consumption of oxygen and production of heat. Thyroid problems, such as an overactive or under-active thyroid, can severely affect metabolism and quality of life.