Estrone
Definition
Estrone (E1) is one of the three primary forms of estrogen. It is often referred to as the "menopause estrogen" because it becomes the dominant form produced by the body after the ovaries cease their primary production of estradiol.
In Depth
Estrone (E1) is a weaker form of estrogen compared to estradiol (E2). While estradiol is the powerhouse of the reproductive years, produced primarily by the ovaries, estrone is produced both in the ovaries and, significantly, in peripheral tissues like body fat (adipose tissue) and muscle.
After menopause, when the ovaries stop producing large amounts of estradiol, estrone becomes the body's primary source of estrogen. This conversion happens through a process called aromatization, where adrenal androgens (male-type hormones like testosterone and DHEA) are converted into estrone. Because significant estrone production occurs in fat cells, women with higher body fat percentages may have higher levels of estrone after menopause than those with lower body fat.
While estrone is weaker than estradiol, it still acts on estrogen receptors throughout the body. However, because it is less potent, it often cannot fully compensate for the loss of estradiol in protecting bone density or preventing hot flashes. Furthermore, excessively high levels of estrone (often driven by high body fat) have been linked to an increased risk of estrogen-sensitive cancers, including endometrial and breast cancer, because it can be converted back into estradiol in certain tissues. Understanding estrone's role in the postmenopausal landscape highlights why metabolic health and body composition are critical components of a healthy menopause transition.
Why It Matters
Estrone is the primary source of estrogen in the postmenopausal body. Monitoring its levels and understanding its source (adipose tissue) provides key insights into metabolic and oncological health after menopause.