Estradiol, estrone and estriol are three forms of the hormone called estrogen. Hormones are messenger molecules that travel through your bloodstream and interact with cells at specific target sites. Estradiol and estrone are produced and secreted by the ovaries. During pregnancy, estriol is produced by the placenta. Throughout a woman’s life, the breasts and uterus as well as the brain, bone, liver and heart are target sites for estrogen molecules. Estrogen levels impact a woman’s reproductive system and physical appearance, bone health and risk for heart disease. Women need estrogen for good health.
Estrogen stimulates the development and maintenance of the female reproductive system along with the development of secondary sexual characteristics. During puberty, increased estrogen secretion heralds noticeable changes such as breast development, pubic and underarm hair growth and the onset of menses. A young girl’s body shape changes with a redistribution of fat to the hips, thighs and buttocks. A growth spurt typically happens during early puberty and can peak by the age of 12. Women have smoother skin and less facial hair than men because of estrogen. Each month during a woman’s childbearing years, estrogen triggers the proliferation of cells within the mammary glands and endometrium, which is the inner lining of the uterus. As a woman approaches her late 30s, her ovaries naturally start producing less estrogen. Fluctuations in hormone levels occur during perimenopause. Once a woman reaches menopause, her ovaries produce much less estrogen.
Pregnancy & Breastfeeding.
Hormones regulate the menstrual cycle. Luteinizing hormone and follicle-stimulating hormone stimulate the ovaries to produce estrogen and progesterone in preparation for possible fertilization. After an egg is released from an ovary, estrogen levels rise and cause the endometrium to thicken. If conception happens, the embryo or fertilized egg implants itself in the endometrium, which is its early source of nourishment. Estrogen causes the milk ducts in the breast to widen and prepare for milk production. A woman needs estrogen if she wants to have a baby and breast feed her baby.
To maintain bone density, your body needs an adequate supply of minerals such as calcium, vitamin D and several hormones including estrogen. A woman needs estrogen to maintain strong bones. Lack of estrogen is a major cause of osteoporosis among menopausal women. Osteoporosis leads to brittle bones and the increased chance of fractures.
Estrogen controls cholesterol levels by raising the "good" high-density lipoprotein cholesterol. Healthy, premenopausal women have high HDL levels and low LDL levels because of estrogen. During menopause, when estrogen levels drop, a woman loses this protection and her risk for developing heart disease increases.