Estrogen is one of the female hormones that help regulates a woman’s passage through menstruation, fertility, and menopause. Estrogen is one of the most powerful hormones in the human body. Some 300 different tissues are equipped with estrogen receptors-chemical sites that make the tissues responsive to estrogen. That means that estrogen levels in the body can affect a wide range of tissues and organs, from the brain to the liver and to the bones themselves. The uterus, urinary tract, breasts, skin, and blood vessels depend on estrogen to stay toned and flexible.
Although we are used to thinking of menarche (the onset of menstruation and fertility) and menopause (the cessation of menstruation and fertility) as single points in life’s journey, they are actually more like peaks and valleys. Estrogen levels start to rise well before menarche, as early as age eight in some girls. The hypothalamus is the prime mover in this process, signaling the pituitary to release hormones; the pituitary, in turn, signals the ovaries to produce more estrogen.
For three or four years, estrogen levels continue to rise, and by age eleven or twelve, they are sufficiently high (along with other key hormones) to begin the menstruation process. Estrogen also sets off the development of the breasts and the growth of hair under the arms and in the pubic region. The body often responds to this new hormonal activity with confusion: oily hair, acne, budding sexual interest, mood swings, and, sometimes, painful menstrual cramps.