There are seven glands in the endocrine system. These glands don’t have ducts. The pituitary gland is also known as the master gland. It hangs at the base of the brain. If the pituitary produces too little growth hormone, a child may have the condition called dwarfism. Too much of this hormone might cause a child to grow into a(n) giant. The parathyroid glands produce a hormone that controls how much calcium is in the blood. The thyroid gland produces hormones that affect how cells use oxygen to release energy in food. The thyroid needs the mineral iodine. The sum of all the chemical reactions that occur in the body is called metabolism.