Steroid hormones are multifunctional messengers to the brain.
Because the brain regulates the endocrine system and also responds to it, the changing environment as well as the experiences of the animal can change and shape properties of hormone-sensitive nerve cells. Depending upon the physiologic status of the organism, the effects of actions of steroid hormones can be trophic or damaging to the nervous system. Future research on the actions of steroids on the brain may advance the notion that the endocrine system has some responsibility for determining the individual traits of an animal in brain function and behavior.