Circulating Estrogen Levels
In men and postmenopausal women, extragonadal sites are the major source for the LOW circulating ESTRADIOL, which is NOT a good indicator of tissue levels and is NOT the body's main driver of estrogenic activity. In fact, estrogen circulation levels actually reflect estrogen which has escaped from metabolism at extragonadal sites of production.
For example, the estrogen responsible for breast cancer development, maintenance of bone mineralization and cognitive function is not circulating estrogen, but rather that which is produced locally at these specific sites within the breast, bone and brain, respectively.
– Circulating, blood ESTRADIOL levels are actually higher in men than postmenopausal women -
✔ In males, concentration is ~2-3 ng/dl compared to postmenopausal women at ~1.5ng/dl. - ESTRADIOL production rate in blood is also significantly higher (25-40 μg/24 h) in men. Male levels of estrogen tend to increase with age (at the expense of TESTOSTERONE) due to increased aromatase activity
✔ Premenopausal women have an ESTRADIOL concentration of ~5.5.ng/dl in days 2-4 of menstrual cycle.
Circulating levels of pituitary and steroid hormones in postmenopausal women compared with levels in postmenopausal women studied during first week of the menstrual cycle (Days 2-4)
(To convert: pg/ml->Ng/dl, divide by 10)