Selected Topics in Thyroid DiseaseAbout This Hardback The thyroid is a gland that produces hormones that help control many vital functions of the body especially metabolism. A medical condition in which the thyroid gland does not produce the right amount of hormones is referred to as thyroid disease. The two major types of thyroid diseases are hyperthyroidism and hypothyroidism. Hyperthyroidism happens when the body makes too much thyroid hormone whereas hypothyroidism is when the