What is the difference between hypothyroidism and hyperthyroidism?

Hypothyroidism refers to an underactive thyroid gland that is producing and secreting less than normal amounts of thyroid hormone. Hyperthyroidism means that there is abnormally high amounts of thyroid in the blood stream. Hyperthyroidism can happen when the thyroid gland either makes or secretes excess thyroid hormone or when people take a higher dose of thyroid pills than they need.