Estriol is a type of estrogen that occurs naturally in the body. There are three different types of estrogen, and for quite some time, estriol has received little attention. This is because it has long been considered to be the weaker type of estrogen as compared to estrone and estradiol. Recent studies, however, may have just found use for the lowly estriol, and it seems that its strength lies primarily in its perceived weakness.

It has been shown in recent researches that topically applied estriol does not elevate the risk of developing breast and endometrial cancers (or cancer of the lining of the endometrium) and other malignancies that are estrogen-dependent. Estriol may exert weaker estrogenic effects, but can still provide the benefits of estrogen. Estriol can significantly decrease the symptoms associated with menopause, like vaginal dryness and hot flashes, as has been shown in studies. Because of this, estriol actually becomes a more viable option for a treatment regimen that entails bio-identical hormone replacement.

There are other benefits from using the so-called weak estrogen as well. Estriol has also been demonstrated to increase bone density, improves heart and circulatory and postmenopausal genitourinary health. This article is written to go over the qualities of estriol and what makes it popular of late.

Estriol and Hormone Replacement Therapy

Estriol is a very plausible treatment for people who are undergoing HRT, or hormone-replacement therapy. In the past, the only thing that is known about estriol is that it is significant only during the gestational period. During pregnancy, estriol levels can go as high up as 1,000 times the level of non-pregnant estriol levels.

The advent of hormonal replacement therapy took place in the sixties. Equine estrogen (Premarin®) and synthetic progestin (Provera®) are just some of the brands that came out and were eventually included in the hormone replacement regimen. As much as 30 percent of women past the menstrual age were taking Premarin® in the 1990s. Along with the increase in the number of women using these hormone replacement drugs came the documented rise in the incidence of breast cancer, cardiovascular diseases and blood clotting disorders, especially when these equine and synthetic hormones were used in conjunction with Prempro®. The medical field took notice, and started to look for a safer, more natural option. The concept of bioidentical hormones thus came into being. This entails the use of an identical, naturally produced hormone, and was started in the 1980s by Dr. Jonathan Wright in Washington in treating menopausal women.

Since then, estriol has been noted to be a lot safer than the equine- and synthetically-derived hormones, which are both implicated in various diseases such as breast and endometrial cancer and cardiovascular disorders. Interest in the new hormonal treated increased steadily. However, many doctors have yet to prescribe estriol, oftentimes dispensing estradiol which is a more potent estrogen and at the same time associated with a number of health risks.

The effects of estriol can be explained by both its pro-estrogenic and anti-estrogenic properties. This interesting combination of characteristics of estriol has been studied by Melamed et al. Researches performed by the group revealed that with the addition of estriol to estradiol, there is a marked decrease in the effects on the cells that can be solely attributed to estradiol. The results have encouraging implications especially with the reduction of carcinogenic risks that are largely associated with the use of the more potent estradiol. With prolonged use, estriol, when used alone, can provide more pro-estrogenic effects, which means that relief of symptoms among postmenopausal women is achieved using estriol. Results of numerous experiments likewise reveal that estriol and tamoxifen, which is a synthetic anti-estrogen drug, are two agents that can render protection from breast cancer secondary to radiation.

Estriol Reduces Cardiovascular Risk

Studies are also suggesting that estriol can provide protection for the heart and the peripheral vessels. In a research authored by Takahashi et al, 2 mg of oral estriol a day administered to women who have had menopause for one year can produce a palpable decrease in the blood pressure among some subjects.1

There is likewise a decrease in the levels of cholesterol and triglycerides, as well as an increase in the levels of high-density lipoprotein among some elderly women who have received oral estriol at a dose of 2mg daily for 10 months. This was determined in a study that included 20 postmenopausal and 29 elderly women.

Estriol Improves Bone Mineral Status in Women

Estriol has likewise been shown to improve bone mineral density levels. According to a Japanese study, there was note of better bone mineral density, less postmenopausal symptoms, and virtually no elevation in the risk of contracting endometrial hyperplasia (otherwise known as the thickening of endometrial lining which may be a precursor to cancer) among 75 postmenopausal women who took 2mg of estriol and 800 mg of calcium lactate everyday for 50 weeks.6

The group of Nishibe also did a study comparing the combined treatment protocol of 2mg/day of oral estriol and 1000mg/day of calcium lactate with only 1000 mg/day treatment with calcium lactate. The study revealed that the postmenopausal and elderly women benefited significantly from the treatment protocol that included estriol in terms of increasing their bone mineral density levels.

Estriol Reduces Brain Lesions in Multiple Scleroris

During pregnancy, estriol levels are elevated. This affects the way the way the immune system of the body responds to various stimuli, and in effect it provides protection from and improvement of certain autoimmune conditions. 9 In a research done by Sicotte et al performed at the Los Angeles Reed Neurological Research Center, high pregnancy estriol doses (8mg/day) administered to non-pregnant women who have multiple sclerosis markedly reduced the amount of lesions on the cerebrum as demonstrated on the MRI. These very lesions increased in amount the moment the estriol treatment was stopped, and which decreased soon after the estriol was resumed. Visualization of brain lesions associated with multiple sclerosis is enhanced with the use of the Gadolinium contrast agent, and an increase in the number of Gadolinium-enhancing lesions imply that there is an increase in the inflammatory reaction that can be attributed to the progression of multiple sclerosis. This makes Gadolinium-enhanced MRI a good study of choice for assessing the progression of multiple sclerosis.

Estriol can Protect Urinary Health in Postmenopausal Women

Estriol also has beneficial effects to the urinary tract. This is certainly good news for postmenopausal women, who are at constant risk of contracting recurrent urinary tract infections and incontinence. Estriol suppositories given intravaginally at a dose of 2mg a day has been shown in a prospective, randomized, placebo-controlled study (which
involved 88 postmenopausal subjects) to reduce the symptoms of incontinence. Aside from this, there is an improvement in the levels of mean maximal urethral pressure and the mean urethral closure pressure, implying that estriol is good for conditions such as incontinence.

Urinary tract infection was also noted to have decreased in incidence in yet another randomized placebo-controlled study. The effects of intravaginal estriol cream, which contains 0.5 mg estriol), applied once a day for two weeks then two times a week for eight months, were compared to the effects of placebo. The study showed that the incidence of urinary tract infection significantly decreased with the use of estriol (0.5 compared to 5.9 episodes every year in the placebo group).