The endocrine system is the collection of glands of an organism that secrete hormonesdirectly into the circulatory systemto be carried towards distant target organs. In humans, the major endocrine glands include the pineal gland, pituitary gland, pancreas, ovaries, testes, thyroid gland, parathyroid gland, and adrenal glands. In vertebrates, the hypothalamus is the neural control center for all endocrine systems. The field of study dealing with the endocrine system and its disorders is endocrinology, a branch of internal medicine.