Estrogen is the major hormone responsible for the characteristics typically thought of as female. Required for proper development of sexual organs, completion of skeletal system, regulation of the menstrual cycle and maintenance of pregnancy, estrogen is extremely important in the growth and development of the female body. During the menstrual cycle, estrogen is secreted by the developing egg follicle and aids in thickening of the endometrium.
Also one of the major hormones of pregnancy, estrogen supports the production of fluid in the reproductive tract which enhance the survival of sperm by slightly neutralizing cervical secretions. Towards the end of pregnancy, estrogen promotes the growth of milk ducts within the breasts and enhances the effect of prolactin (major hormone responsible for lactation in the female).
As a woman ages and she enters Menopause, her estrogen levels begin to decline. For that reason, some physicians may prescribe estrogen replacement therapy, to minimize some of the symptoms experienced. Estrogen is also the main hormone found in the birth control pill. Each pill is different, containing varying amounts of estrogen and/or progesterone.