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 regulates the body's metabolism. The parathyroid glands regulate the body's calcium balance.

• Thymus. The thymus is located in the upper part of the chest and produces (white blood cells, called T-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 behind the stomach. It produces hormones for digestion and metabolism. Among the major hormones produced by the pancrease is insulin, which is essential to regulate blood sugar levels.

• Ovary. An ovary is located on each side of the female's uterus, below the opening of the fallopian tubes, which extends from the uterus to the ovaries. In addition to containing the egg cells necessary for reproduction, the ovaries also produce estrogen and progesterone.

• Testis. Two testes are located in a pouch (the scrotum) that hands suspended outside the male's body. The testes produce testosterone and sperm.