Many steels add to the iron-steel mix other metals that give the entire substance desirable properties such as strength, heat resistance, or flexibility. Steel is considered a mixture rather than a compound because the iron does not chemically bond with the carbon and other components.
Some of estrogen's effects include: 1  Increasing serotonin, and the number of serotonin receptors in the brain. 2  Modifying the production and the effects of endorphins, the feel-good chemicals in the brain. 3  Protecting nerves from damage, and possibly stimulating nerve growth.
As an example, despite estrogen's apparently positive effects on the brain, many women's moods improve after menopause, when estrogen levels are very low. Some experts believe that some women are more vulnerable to the menstrual cycle's normal changes in estrogen. They suggest it's the roller coaster of hormones during the reproductive years that create mood disturbances.