ESTROGEN PRODUCTION
The term “estrogen” is used to collectively describe the
female hormones, the most potent of which is estradiol. The
other important—but less powerful—estrogens are estrone and
estriol. Estrogens affect the growth, differentiation, and function
of diverse target tissues—not only those involved in the reproductive
process, but tissues throughout the body. Estrogens play
an important role in bone formation and maintenance, exert cardioprotective
effects, and influence behavior and mood.
Although estrogen is best known for its critical role in female
reproduction, less well known are the important actions of estrogen
in male tissues, such as the prostate and testes.1,2
In women, estrogens are synthesized from cholesterol in the
ovaries in response to pituitary hormones. In an adult woman
with normal cycles, the ovarian follicle secretes 70 to 500 μg of
estradiol per day, depending on the phase of the menstrual cycle.
Estradiol can be converted to estrone and vice versa, and both
can be converted to the major urinary metabolite, estriol.
Estrogens are also produced by the aromatization of androgens in
fat cells, skin, bone, and other tissues. After menopause, most
endogenous estrogen is produced in the peripheral tissues by the
conversion of androstenedione, which is secreted by the adrenal
cortex, to estrone. In addition, some estrogen continues to be
manufactured by aromatase in body fat, and the ovaries continue
to produce small amounts of the male hormone testosterone,
which is converted to estradiol. The total estrogen produced after
menopause, however, is far less than that produced during a
woman’s reproductive years.1,2
A brief description by DOUGLAS C. HALL, M.D.