No single “normal” estrogen level is possible for women. Normal levels can fluctuate, depending on the age of the woman and whether she is menstruating, pregnant or lactating. They can even change from minute to minute, according to WebMD. Estrogen is not a single hormone, but rather a group of hormones responsible for sexual functions, bone health and fertility.

Types

There are three primary estrogen hormones. They are estradiol, estriol, estrone. Estradiol is important in fertility. Produced by the ovaries, it aids in egg maturation and egg release. Estradiol also is important for bone density. Estriol is vital for fetal development and is produced by the placenta. Estrone is also produced by the ovaries and is the hormone primarily responsible for regulating the menstrual cycle. All three are also produced by fatty tissue.

Significance

Estrogen levels in women are best measured on the third day of her period, according to EarlyMenopause.com. Normal levels fall anywhere between 25 to 75 pg/ml. These numbers will rise to as high as 407 pg/ml directly before ovulation. In most cases, women with a number of 30 pg/ml on the third day of her period are considered menopausal.

Considerations

Low levels of estrogen can be caused by external and internal factors. Because these hormones are produced by fatty tissue, anorexic or very athletic women with little body fat may have low levels of the hormones. Menopause and other hormonal problems, such as polycystic ovarian syndrome, can also cause low levels of estrogen. These low levels can result in headaches, hot flashes and night sweats, according to BabyHopes.com. Low estrogen levels can also result in osteoporosis (especially during menopause), irregular menstruation or amenorrhea, infertility and even miscarriage.

Misconceptions

Estrogen is not just for women. Men also produce low amounts of estrogen hormones, according to MSN Health. Estrone and estradiol are both produced by the adrenal glands and fatty tissues. Estradiol is also produced in the testes. These small amounts promote hormonal balance in a male.

Expert Insight

Experts are divided as to whether estrogen therapy — the process of taking supplemental estrogen when hormone levels are low — is beneficial or not, according to MedicineNet.com. Although estrogen patches and gels can greatly reduce headaches and hot flashes, there are sometimes side effects, some of which can be serious. These include breast pain and a slightly increased risk of breast and endometrial cancer.