Why Is It Important To Measure Estradiol Blood Levels?

 

Many women who initially see me for menopause have never had their estradiol level checked. Their previous physician may have diagnosed menopause with an elevated FSH, but usually no further tests are done. I’d like to go through various reasons why I believe it is important to monitor estradiol levels.

1. ESTROGEN IS A TWO-EDGED SWORD

I describe estrogen as a two-edged sword because it can be both protective and harmful depending on how your body uses it and on the amounts and duration of estrogen exposure. Endogenous estrogen refers to the levels of estradiol that a woman’s own body produces before menopause. Early in the book I outlined how estrogen is essential to many cellular functions throughout the body. In Chapter 22 – Risks of NOT Taking Estrogen, I listed the many symptoms and degenerative consequences that can result from a low estrogen state.

On the other hand, estrogen excess throughout a woman’s life is associated with increased risks of cancer. An increased risk of breast cancer is associated with longer exposure to endogenous estrogen, i.e. early menarche (starting your periods at an early age) and later menopause. Higher estrogen states seen with obesity increase the risk of breast cancer even more. Studies show women with a body mass index (BMI) over 35 have a twenty-fold increased risk of endometrial cancer.

Estrogen, estrone and testosterone can be produced from fat cells in obese postmenopausal women. These obese women also have lower production of a substance in the blood called sex hormone binding globulin (SHBG). SHBG serves as a carrier protein for storing estrogen in the blood. Lower levels of SHBG results in higher levels of available estrogen that thereby increases their estrogen exposure. In the Nurses’ Health Study of a subset of women on no HRT, an increased risk of breast cancer was seen in women with the highest endogenous estradiol compared to those with the lowest estradiol. A similar increased risk was seen in women on no HRT with the highest endogenous level of testosterone. However, in women on HRT with low testosterone, studies show that adding testosterone can be beneficial in lessening the risk of breast cancer.

These potentially protective and harmful effects of estrogen go back to the basic tenet of any hormone – adverse symptoms can occur with deficiency or excess while optimal function develops with the right level. I see this as an affirmation of the need to respect the balance among the different sex hormones. Monitoring estradiol and testosterone blood levels enables us to prevent a deficient state while guarding against excess levels. This is a standard practice when physicians prescribe thyroid hormone. Why should it be any different for estrogen and testosterone?

2. VARIABILITY OF TOPICAL ABSORPTION

While levels are consistent within a given individual, tremendous variability in the efficiency of absorption can be found from one woman to another and this constitutes another reason to measure blood levels. In a study of women given identical doses of topical estradiol there was considerable variation in blood levels with estradiol increases above baseline differing as much as 90 pg/ml from one woman to another. Studies have even shown differences in absorption when changing women from one patch to a different brand of the same dose. Despite such variations, absorption of topical estradiol is more stable and consistent than oral estradiol which peaks at 4 to 5 hours and is non detectable by 8 to 10 hours.

This phenomenon of variable absorption with topical patches, gels and creams has been documented in numerous studies. Importantly, estradiol blood levels tend to be consistent within a given woman once appropriate levels are achieved and frequent dosage changes are not generally required. Annual monitoring of estradiol blood levels is generally adequate to ensure therapeutic levels. With increasing age of the woman, drug metabolism may be slower, requiring dose reduction to prevent excess estradiol levels.

Since I routinely monitor blood estradiol levels, I have seen such variation in topical absorption in the thousands of women I have managed. This may also explain why some women who first start topical estradiol sometimes give up saying “it doesn’t work” and they switch to pills. Since you have learned of the lower risks from topical estradiol, it is worthwhile to persist in finding a topical product that works for you. In my clinical experience of managing over 100,000 female patient visits, I’ve found very few women who could not be managed with topical estradiol.

In general, thin women require higher estradiol doses while obese women with endogenous stores of estrogen in fat generally can be managed with a lower dose. Higher climate temperature in summer months may increase the need for higher doses of topical estrogen especially in women who are outdoors a lot and are very physically active. Women who take long hot baths will likely reduce estrogen absorption from estradiol patches because the hot water leaches estradiol from the patch. Taking showers does not have this effect. If a woman insists on long, hot, baths, she is best managed with topical gels and creams.

When a pharmaceutical drug is developed, in order to receive FDA approval, the manufacturer must show proof that their product has effectiveness and achieves significant blood levels. The pharmacology term for this is the “drug-response curve.” Studies are done to establish the optimal dose that will achieve certain blood levels and the desired therapeutic effect with the least adverse side effects.

Tomorrow: Why You Can’t Just Go By ‘How You Feel!’ – Read Part 2

 

The content of this blog series is for informational purposes only and is not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. This blog series may discuss nutritional products and protocols that have not been evaluated by the U.S. Food and Drug Administration. These products or the information contained on this website is not intended to diagnose, treat, cure or prevent any disease. All website content is © Copyright 2012 by Marina Johnson MD – All Rights Reserved

Excerpt from “Outliving Your Ovaries” © 2012 by Marina Johnson MD. Dr. Johnson was a medical writer and pharmacist before medical school and utilized these skills to research 450 medical journal articles to develop her book. She has no financial conflicts of interest or ties to any pharmaceutical company. Her only objective is determining the most effective, safest therapy for patients.

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All website content © Copyright 2011 by Marina Johnson, M.D., F.A.C.E. - All Rights Reserved

The content of this website is for informational purposes only and is not intended to be a substitute for professional medical advice,diagnosis or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. This website may discuss nutritional products and protocols that have not been evaluated by the U.S. Food and Drug Administration. These products or the information contained on this website is not intended to diagnose, treat, cure or prevent any disease.