Knowledge center. Hyperthyroidism, also known as overactive thyroid, is a medical condition caused by an abnormally high level of thyroid hormone in the bloodstream. The thyroid gland produces an excessive amount of thyroid hormones.The thyroid gland is located in the neck.raves' disease. It is the most common cause. Graves' disease is an autoimmune condition in which the body's immune system mistakenly targets the thyroid gland and causes it to produce too much thyroid hormone.
DEFINITION of 'Federal Reserve Bank'. The central bank of the United States and the most powerful financial institution in the world. The Federal Reserve Bank was founded by the U.S. Congress in 1913 to provide the nation with a safe, flexible and stable monetary and financial system.
Federal Reserve Banks. 1  1st District, Boston. Connecticut (excluding Fairfield County), Massachusetts, Maine, New Hampshire, Rhode Island, and Vermont. 2  2nd District, New York. New York State, twelve counties in northern New Jersey, Fairfield County in Connecticut, Puerto Rico, and the Virgin Islands. 3  3rd District, Philadelphia.