Hormones are various substances secreted by glands into the bloodstream which alter the activity and sometimes the structure of organs and tissues, thereby affecting health and well-being. Even before birth, hormones control many bodily processes. Growth hormones stimulate growth and development in children; sex hormones trigger sexual development in teens; and declines in certain hormones with age, lessen muscle mass, and reduce time spent sleeping. At any age, over-production or under-production of these hormones may adversely affect our health. Hormone-secreting glands include the sex glands (ovary and testis), the adrenal glands, the pancreas, the thyroid, and the pituitary, the “master gland.” Hormones are also made in your brain; these hormones affect your mood, psychological status, and energy level and also regulate the pituitary gland. Furthermore, different glands make more than one hormone. For example, the thyroid makes both T4 and T3, and the ovaries make different types of estrogens, estrone (E1), estradiol (E2) and estriol (E3). Glands and the hormones they produce are listed in this Table.