2. Extremes of Mood
People suffering from thyroid dysfunction also may observe a significant change in their usual demeanor and attitude. Those with hypothyroidism, when decreased levels of thyroid hormones are produced, more commonly have depression, apathy, cognitive dysfunction, or psychomotor slowing. With hyperthyroidism, on the other hand, when there is an overproduction of thyroid hormones, there may be anxiety, restlessness, and irritability; the body is always working overtime, making people hyper and unable to relax.