The endocrine system consists of specialized groups of cells called glands that make, store, and release regulating chemicals called hormones directly into the bloodstream to regulate how the body functions. Some of these endocrine glands include the adrenals, chemoreceptor organs, gonads (testis and ovary), hypothalamus, pancreatic islets, parathyroid, pineal, pituitary, and thyroid. These glands secrete hormones that travel through the circulatory system to regulate the various body systems.