About Estradiol

Estradiol is the most active form of estrogen in the human body.

As well as the being one of the most important "female hormones" which is responsible for a normal monthly cycle, estradiol is known to support normal function in quite a number of important physiological processes including -
1. bone mineral density & osteoporosis prevention's
2. proper heart and blood vessel health & arteriosclerosis prevention.
3. Mood
4. sex drive
5. thyroid function
6. skin elasticity (which decreases without estradiol and causes thin skin and wrinkles)
7. and fertility

Peri- and post-menopausal women may monitor the decreasing levels of this hormone that occur with aging. Cycling women experiencing PMS symptoms that
may be due to a hormonal imbalance may also monitor estradiol.

In men estradiol does not play as important a role as it does in women, though men also have a small amount of estradiol normally in their bodies. The amount of testosterone that men have usually does not allow estradiol to have any significant physiological effects on the body. If the amount of estradiol compared to testosterone increases, then men can notice certain symptoms such as weight gain especially in the midsection, development of enlarged breasts (gynecomastia), decreased sex drive, and many of the signs of low testosterone.

Certain medications and drugs, chronic alcoholism and other chronic health conditions can result in increased estradiol levels in men.

In women, estradiol is a steroid hormone produced primarily by the ovaries and adrenal glands. Estradiol has a direct affect on the function of the reproductive system, the nervous system, the cardiovascular system and the skeletal system.

Blood sugar levels, skin and other tissues and functions are also significantly influenced by estradiol.

Though proper estradiol levels are critical for the prevention of osteoporosis, the actions of this hormone extend far beyond bone health.

Therefore it is crucial that proper levels also be maintained in all women.

The Menstrual Cycle and the Endometrium

Progesterone prevents development of endometrial cancer 1. Low progesterone with unopposed estrogen may be one cause of dysfunctional uterine bleeding 2. Progesterone may help decrease uterine contractions, cramping and pain 3, 4.

The Vagina & Urinary Tract

Excessive progesterone may increase urinary incontinence and even counteract the beneficial effects of estrogen in maintaining urinary control 5, 6, 7, 8.

The Libido

Excessive progesterone may decrease libido due to antiestrogen and anti-androgen effect 9, 10. As well as decreasing libido, excessive levels may induce depression 11.

Blood Sugar & Insulin

While estrogens help the cells of the body utilize glucose more efficiently by making them more sensitive to insulin, progesterone can cause a decrease in insulin sensitivity, having an effect on blood sugar that is similar glucocorticosteroids 12. This interference with the action of insulin can interfere with normal glucose uptake and cause insulin resistance 13, 14, 15, 16, 17.

The ability of progesterone to interfere with proper function of insulin and glucose has since been associated with gestational diabetes 18, 19, 20 as well as hormone replacement therapies 21,15, 22, 12 and has been been observed in both synthetic & non-synthetic progesterone 20, 23, 24, 12. Even the high progesterone levels which occur naturally during the luteal phase can induce insulin resistance in some women 21, 16.

The Brain – Mood & Memory

Progesterone and its metabolites result in increased relaxation and reduced anxiety in a way that is similar to the effects of benzodiazepines 25, 26 by a direct effect on neurotransmitter receptors called Gamma-AminoButyric Acid type A (GABAA) receptors 27. When progesterone levels drop a woman can experience withdrawals similar to the withdrawal seen with benzodiazepine, barbiturate, and alcohol withdrawal 29.

Excessive levels may cause decreased coordination, slowed reflexes, depression and impaired memory and reasoning skills 30, 31, 32, 33, 34. The sedating effects of excessive progesterone can cause drowsiness and even induce sleep 35, 32, 36. The nerve calming effect of progesterone is so pronounced that both natural progesterone and medroxyprogesterone have both been shown to decrease seizures in women with epilepsy 37, 38.

Progesterone has a protective, stimulating effect on breathing patterns during sleep, resulting in decreased incidence of sleep apnea, a serious condition in which the body is deprived of oxygen 39, 40, 41, 42.

The action of progesterone on GABAA receptors have been associated with an increase appetite and food intake 43, 44, 45.

Estrogen refers both to natural estrogen hormones in the body and estrogen products used in medications. The main forms of estrogen found in women's bodies—endogenous estrogen—are:

estradiol, the main estrogen made by women’s ovaries before menopause (also described as 17-beta estradiol and E2)

estrone, a weaker estrogen produced both in the ovaries and in fat tissue from other hormones, and the main estrogen found in women after menopause (E1)

estriol, the weakest of the three main forms of estrogen, made in the body from other estrogens (E3) and found in utero with growing fetus.

The amount of these estrogens in the body varies over the course of the menstrual cycle. After menopause, estrone becomes the predominant endogenous estrogen in women’s bodies even though the ovaries continue to produce small amounts of estradiol, as do the secondary hormone-production sites. The adrenal gland continues to produce androstenedione, which is converted to estrone and estradiol in body fat and in muscle and skin cells. In addition, the ovaries continue making small amounts of testosterone, which can be converted to estradiol, but often is not in significant amounts.

How does estrogen function in the body?
Estrogens, particularly estradiol, are powerful female hormones that make a girl develop into a woman capable of reproduction. Whether from your own ovaries or from an external source, estrogens work in the body by traveling in the blood to body tissues where there are estrogen receptors. Estrogen receptors are found in the brain, breasts, heart, blood vessels, uterus, vagina, bladder, liver, bones, skin, and gastrointestinal tract. Estrogen molecules bind, or attach, to estrogen receptors much like a key fits into a lock, and this leads to effects that vary from one body part to another.

Not all parts of the body have estrogen receptors, and not all estrogen receptors are alike. Estrogen receptors in bone tissue are not the same as estrogen receptors in breast tissue, for example. There are other factors that influence the differing effects of estrogen in different parts of the body, but not a great deal is known about these other factors.

What are the effects of lower estrogen levels?
Because estrogens have important effects on so many body tissues, it is not surprising that when a woman’s estrogen levels drop (especially when they drop suddenly), there may be negative or potentially negative effects. One of the most noticeable effects, of course, is the end of menses, the monthly periods. The end of menses is due in part to estrogen levels that are too low to stimulate the lining of the uterus (endometrium).

In addition to the end of menses, significant estrogen loss can also lead to:

hot flashes and night sweats with disturbed sleep
vaginal dryness and loss of elasticity of vaginal tissue , elasticity of skin, blood vessels, heart vessels
increased urinary tract infections and problems with urinary incontinence (difficulty holding one’s urine)—although childbirth appears to be the most important cause of incontinence in postmenopausal women
loss of sexual desire and function
changes in mood, or depression
memory problems and possible increased risk of Alzheimer’s disease
breast changes—loss of firmness
skin changes—thinner skin, less collagen and moisture in the skin
loss of bone density—may eventually lead to osteoporosis
increase in cholesterol levels—may increase risk for heart disease
loss of numerous beneficial effects of estrogen on body organs and systems
Estrogens used in ERT, HRT and NHRT

Estrogen products may provide either a single type of estrogen or mixed estrogens. The most commonly prescribed form of estrogen for HRT in the U.S. for many years has been a mixture of estrogens extracted from the urine of pregnant mares (Premarin, and the estrogen in Prempro and other estrogen products that begin with Prem-). Prempro is the combined synthetic estrogen/progestin formulation that was found in the WHI study to be associated with a somewhat increased risk of breast cancer, heart attack, stroke, and blot clots.

There are many alternatives to Premarin available to women today. Other estrogen products, including bio-identical estrogens, are made in the laboratory from plant materials, usually wild yam or soy. Estrogens can be taken in pill form or as sublingual (under the tongue) tablets. There are also estradiol skin patches (transdermal estrogen), and some estrogen products can be used in the vagina. An estradiol skin gel (EstroGel) is available in many countries including Canada and the U.S. An estrogen nasal spray is being tested. Most estrogen products delivered through the skin are bio-identical estrogens, but some oral and vaginal estrogens are not (e.g., Premarin, Ogen, Cenestin, Premarin vaginal cream). The estrogen used in transdermal patches is bio-identical estrogen (estradiol); however, the estrogen used in the contraceptive skin patch (Ortho Evra) is a synthetic estrogen.

Examples of estrogen products
Oral (pills): Estrace, generic estradiol, Ogen, Premarin, Cenestin
Transdermal: Vivelle, Climara, Alora, Estraderm (skin patches)
EstroGel (now available in the U.S.)
Vaginal: VagiFem, Estring
I prefer to use the Wiley Protocol transdermal estrogen because it is bioidentical and is the only standardized cyclic hormone therapy available at this time to replace hormones the way young cycling female hormones are.

Estriol is not often used in HRT, although it is possible to have an estrogen cream that contains estriol made to order by a compounding pharmacy. Estriol, while much weaker than estradiol, is still able to cause systemic effects on the user, and studies have found that oral estriol can stimulate the endometrium. Vaginal estrogens are less likely to cause systemic effects and are sometimes effective for restoring vaginal and urogenital tissues to premenopausal conditions and reducing urinary tract infections.

Different products may have somewhat different effects and side effects. Oral estrogens seem to have more side effects than estrogens delivered through the skin or the vagina, apparently due to the "first pass" through the liver that occurs when drugs are taken by mouth.

The differences between oral and transdermal estrogens
Oral estrogens are quickly broken down by the liver, and this "first pass" through the liver seems to be responsible for certain side effects as well as for the positive effects of oral estrogen on cholesterol levels, lowering LDL (the "bad" cholesterol) and raising HDL (the "good" cholesterol). Oral estrogen sometimes raises triglycerides (another type of blood fat) and women who have high triglyceride levels should be aware of this.

Transdermal estrogen given in the doses I prescribe can raise HDL and lower LDL cholesterol, and it does not affect triglycerides, so it may be a better choice in women with elevated triglyceride levels. Avoiding the first pass through the liver also may prevent the increased risk of blood clots and gallbladder problems associated with oral estrogens.

UPDATE: Results of a study reported in the Journal of the American College of Cardiology (April 2003) show that Premarin pills, a form of oral estrogen, increase C-reactive protein (CRP) in the blood, while Climara, an estrogen skin patch, does not. CRP is a marker of inflammation in the blood that has been found to be a heart disease risk factor. Read Could Heart Risks of Estrogen Replacement Be "Patched" Up? for more information. The study confirms earlier research showing that transdermal estrogen does not raise CRP levels in the blood, while estrogen pills do (Vehkavaara S et al., 2001).

Transdermal estrogen and oral estrogen have differing effects on androgens in the body. Oral estrogen lowers free testosterone and can lead to androgen deficiency (affecting libido among other things), while transdermal estrogen has little effect on testosterone levels. Transdermal estrogen may offer other advantages over oral estrogens, although more research is needed.

I have over 500 women on transdermal estrogen and progesterone using the Wiley Protocol who are doing awesome. I've been tracking their progress since 2008 and have amazing results and data showing how replacing your hormones to reflect what your hormones do in young cycling women restores health and well being.

Call my office in Wilmington (815) 476-5210 or Lombard (630) 627-3700 to set up an appointment or email me at