The thyroid is a small butterfly-shaped gland inside the neck that produces two hormones that travel throughout the body. According to the Hormone Health Network, the thyroid regulates the body’s metabolism and can influence any organ in the body. A thyroid that is overactive (producing too much thyroid hormone) results in a disorder called hyperthyroidism. Likewise, a thyroid that is underactive (producing too little thyroid hormone) results in a disorder called hypothyroidism. Read on for more about the symptoms of hyper- and hypothyroid disease.