Estrogen Side Effects and Risks

Estrogen side effects and risks are a concern for all women, who are considering Hormone Replacement Therapy (HRT or HT). There is a lot of confusing information about HRT risks because there are still a lot of unanswered questions.

Additionally there is a battle raging between traditional medical providersand the proponents of bioidentical hormone therapy.

Traditional medical providers say that hormone therapy should be used only to help women get over the worst menopause symptoms. But providers of bioidentical therapy claim that (natural) hormones can safely be used to fight aging.

Estrogen Therapy Risk  – The Background

Discussion about estrogen side effects and risks started with the results of the Women’s Health Initiative. This study surprisingly showed an increased risk of heart attacks, strokes and breast cancer, which led to a huge drop in the prescription of estrogen (mostly Premarin and Prempro, which are still the most prescribed form of HRT).

The results put an end to the recommendation of hormone therapy for anything other than short-term use to alleviate menopause symptoms.

To date we don’t know for sure if at least some of the results stem from estrogen risk or the design of the study. This study was designed to provide scientific evidence for the benefits of long-term hormone replacement.

The researchers wanted to confirm that estrogen could be used as a preventive treatment for age related illnesses for post-menopausal women.The study didn’t try to answer the risk and benefits of estrogen for the treatment of menopause symptoms, which is how most doctors use HRT today.

In a nutshell, the jury is still out if the risks are associated with:

  • Estrogen itself
  • Estrogen in pill form that passes through the liver
  • Estrogen that contains Equilin (Horse Estrogen)
  • Long-term use of estrogen

One risk factor that scientist have isolated is the importance of age when women start with the estrogen supplement. The risk increases, the older a women is when she starts with the hormone therapy.

There appears to be much less risk when women start with a hormone replacement in their 50s, close to the age of their actual menopause, andstay on it for only a few years.

But the risk increases the longer a woman is past menopause before starting with estrogen therapy, and with the length of time a women stays on estrogen supplement.

To date, all long term studies used conjugated estrogen in pill form, namely Premarin (containing sodium estrone sulfate and sodium equilin sulfate).

But today women have other options that do not use this form of the hormone:

  • Forms that are identical to the structure of the estrogen in the body
  • Forms that avoid the metabolism in the liver.

Newer studies are underway to find out more about the estrogen side effects and risks associated with these forms of hormone therapy.

Bioidentical doctors believe that using natural hormones are safe and avoid the estrogen side effects and risks associated with synthetic hormones. Moreover, they say that hormone levels can be balanced to reflect those of much younger women still in their reproductive years.

Most conventional doctors and scientist say that this idea is dangerous, unsubstantiated and nothing but a marketing tool to sell the anti-aging benefit of some forms of hyped bioidentical therapies – which have become a billion dollar industry. (Bioidentical hormones that are compounded in a pharmacy are typically 3-4 times more expensive that conventional prescriptions. Add to this the required testing, and treatment can be very pricey. )

The truth is that no long-term studies have been conducted to proof that using bioidentical hormones long-term are safer and will avoid estrogen side effects and risks.

Health Risks Associated with Estrogen
  • Increased risk of deep vein thrombosis and blot clots in the lungs. This risk is rare and higher for women who smoke or have a family history of thrombosis.
  • Uterine cancer for women who have a uterus and are taking estrogen only. Women who did not have a hysterectomy should always take progesterone to balance the estrogenic effects.
  • Breast Cancer risk increases slightly but goes up the longer estrogen is used (especially after 5 years of use). Estrogen stimulates cell growth, especially in breast tissue.
  • Stroke and heart attack risk increases because estrogen increases the clotting factor of the blood. This occurs mainly with the oral hormone because it passes through the liver and changes its form. Newer forms of estrogen therapy, using skin patches or creams etc, avoid this risk to a great extend. Women with elevated risk of stroke are advised not to use estrogen.

If you have severe symptoms that interfere with your life and you have no history of breast cancer or stroke, hormone therapy may be the right treatment. But it is doubtfull, that it can make you look and feel forever like 30 (sorry Suzanne Sumers).

Estrogen Side Effects

Severe side-effects are more common if you are taking conjugated estrogenorally (like Premarin pills).

Synthetic estrogen contains not only the active hormones (mostly in the form of estrone and equilin sulfate) but also other synthetic additives. It is difficult to determine if the side effects are caused by the synthetic estrogen, the dosage or the additives.

(My personal experience with Prempro* reflects this. Within three days of starting on the 0.625 mg/2.5mg dosage I started feeling worse, plus my feet where swollen to double the size – it was very frightening. After stopping the pills, the symptoms went away. *Prempro has not only conjugated estrogen, it also has Progestin – a synthetic progesterone.)

Check our section on estrogen dominance for a quick check if your side effects could be caused by high levels of estrogen.


Estrogen side effects include:
  • Vaginal bleeding (if outside of cyclical therapy w/ progesterone) can occur, especially for the first couple of months. If symptoms persist or the bleeding gets heavy, your doctor will check if there is no abnormality in the lining of the uterus. If results are normal, usually the dosage needs to be adjusted.
  • Nausea can occur early in the therapy and should go away after a short while. This is mainly a side-effect of oral conjugated estrogen (Premarin Tablets), which contains several other ingredients that can cause nausea.
  • Fluid retention can occur because estrogen affects the cell fluid levels. This is especially true for the oral form. If fluid retention is severe, see your doctor right away.
  • Breast pain is common at the start of estrogen therapy. However, if it persists for more than a few days, it could be sign of too much estrogen. Talk to your doctor about lowering the dosage.
  • Skin irritation is a common side effect of the estrogen patch. Avoid sun bathing or direct heat to the patch because this can cause the patch to release the hormone faster.
  • Estrogen withdrawal symptoms include headaches and return of hot flashes and nightsweats. Hotflashes can be severe until the body adjusts to the lower hormone levels.

Typically the synthetic versions have more estrogen side effects than the natural form but your side effects could also come from a dosage that is too high.


Exclamation_39-39 (1)In rare cases estrogen can have severe risks and side effects- see a Doctor immediately if you have severe abnormal symptoms because this could be a sign of a dangerous health condition.

These symptoms include unexplainable vomiting and nausea, swelling of feet and ankle, yellowing of the eyes, joint and muscle pain.

Because of the many options (patches, pills, rings and natural vs synthetic), you and your doctor may have to experiment a bit to find which form of therapy works best for you.


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