The following are integral parts of the endocrine system:
Hypothalamus. The hypothalamus is located in the brain, near the optic chiasm. It secretes hormones that stimulate or suppress the release of hormones in the pituitary gland, in addition to controlling water balance, sleep, temperature, appetite, and blood pressure.
Pineal body. The pineal body is located below the corpus callosum, in the middle of the brain. It produces the hormone melatonin, which regulates the sleep cycle and natural circadian rhythm.
Pituitary. The pituitary gland is located at the base of the brain. Usually no larger than a pea, this gland controls many functions of the other endocrine glands.
Thyroid and parathyroids. The thyroid gland and parathyroid glands are located in front of the neck, below the larynx (voice box). The thyroid plays an important role in the body's metabolism. Both the thyroid and parathyroid glands also play a role in the regulation of the body's calcium balance.
Thymus. The thymus is located in the upper part of the chest and produces T-lymphocytes (white blood cells that fight infections and destroy abnormal cells).
Adrenal gland. An adrenal gland is located on top of each kidney. Adrenal glands work hand-in-hand with the hypothalamus and pituitary gland to produce cortisol and other hormones important for normal metabolism.
Pancreas. The pancreas is located across the back of the abdomen, behind the stomach. The pancreas plays a role in digestion, as well as hormone production. Hormones produced by the pancreas include insulin, which regulates levels of blood sugar.
Ovary. A female's ovaries are located on both sides of the uterus, below the opening of the fallopian tubes (tubes that extend from the uterus to the ovaries). In addition to containing the egg cells necessary for reproduction, the ovaries also produce estrogen and progesterone.
Testis. A male's testes are located in a pouch that hangs suspended outside his body (the scrotum). The testes produce testosterone and sperm.