Hormones are produced and released into the bloodstream by a variety of endocrine glands including the testes, the ovaries, the pancreas, the adrenal glands, the thyroid, the parathyroid, the thymus, the pituitary gland, hypothalamus and pineal gland. Others may be well-known but not readily identified as hormones.
All vertebrates have an endocrine system.
For more information, see the Environmental Estogens section of Envinronmental Concepts Made Easy. The endocrine system and nervous system work together to control bodily functions and to relay information and instructions throughout the body. They also play an important part in the normal development of the growing fetus. In the womb or egg, hormones guide the development of sexual characteristics, the immune and nervous systems, the brain, behavioural characteristics and growth. Thyroid hormones, for instance, are essential for brain development.