This document discusses different thyroid diseases including hyperthyroidism, hypothyroidism, and thyroiditis. Hyperthyroidism is when the thyroid produces too much hormone and can cause symptoms like weight loss, palpitations, and heat intolerance. Hypothyroidism is when the thyroid does not produce enough hormone and results in fatigue, weight gain, dry skin and hair loss. Thyroiditis refers to inflammation of the thyroid and can be acute, subacute like viral thyroiditis, or chronic like Hashimoto's thyroiditis.