Endocrine glands are ductless or tubeless organs or groups of cells that secrete hormones directly into the bloodstream. The endocrine glands are part of the endocrine system and include the pineal gland, pituitary gland, pancreas, ovaries, testes, thyroid gland, parathyroid gland, hypothalamus and adrenal glands. The endocrine system maintains homeostasis, controls the growth and development, controls metabolism (body energy levels), reproduction, response to stimuli (stress and/or injury).