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.
The role of estrogen is super-important: It helps to stimulate hormone production in the fetus's adrenal gland, it stimulates growth of the adrenal gland, and it enhances the mother's uterus, enabling it to respond to oxytocin (another pregnancy hormone; see below).