The endocrine system is made up of glands that secrete hormones directly into the bloodstream to regulate various bodily functions. The major endocrine glands include the pituitary gland, which triggers other glands, the thyroid gland for growth and development, and the ovaries and testes, which produce sex hormones like estrogen and testosterone. These glands work throughout life to regulate metabolism, organ function, growth, sexual development, and other processes.