Impact of hormone replacement therapy on endogenous estradiol metabolism in postmenopausal women

The WHO claims estrogens are 'carcinogenic': is this true?

Estrogens are in the list of carcinogenic chemicals from the World Health Organization (WHO). However, estrogens require additional factors such as stromal factors or progestogens to increase the ratio of proliferation/apoptosis for initiation of replication errors and consequent mutations to occur. These mutations require at least 5-10 years to develop into clinically detectable cancer, whereby this review is focused on breast cancer. The US National Cancer Institute highlighted a second mechanism of carcinogenicity: certain estrogen metabolites are capable of inducing DNA damage, even in low concentration. They can be assessed in the tissue and circulation. However, those deleterious reactions require excessive unrestricted oxidative cell stress, for example in industrial areas with heavy pollution. We have shown that this can be avoided using transdermal instead of oral estradiol treatment, especially important in smokers. The spectrum of metabolites is also influenced by other exogenous factors such as nutrition, physical activity and certain diseases. Reduction of breast cancer risk as demonstrated in the Women's Health Initiative (WHI) was explained by pro-apoptotic estrogen effects working after a certain 'time gap'. In addition, certain estrogen metabolites are carcinoprotective, if no genetic polymorphisms would impair their beneficial activities. Thus, since additional factors are required for both main pathways of carcinogenicity and because estrogens can even have carcinoprotective effects, we cannot agree with the statement from the WHO.

Benefits and risks during HRT: main safety issue breast cancer

To assess the benefits and risks during hormone replacement therapy (HRT) in postmenopausal women, the only placebo-controlled study testing clinical endpoints with high statistical power has been the Women's Health Initiative (WHI). Although this trial, conducted mainly in older high-risk women, might not reflect the practical conditions for the normal use of HRT, the WHI for the first time provides the main risks in relative as well as in absolute numbers, which are venous thromboembolism and breast cancer, and in older women also myocardial infarction and stroke. Proven benefits such as treatment of climacteric symptoms, reduction of osteoporotic fractures and decrease of colon cancer risk seem to be only important for younger women, because only with early start of HRT cardiovascular risks can be reduced. Reduction of cardiovascular risks can be achieved using transdermal HRT, which, however, was not tested in a placebo-controlled study design similar to that in the WHI. This review focuses on the results of the WHI, comparing different age groups, and in general especially on the main fear of women, risk of breast cancer, which has been defined as a special project between two universities, a close collaboration of a German and Chinese research group.

Urinary 2/16 estrogen metabolite ratio levels in healthy women: a review of the literature

This is a summary of the published literature on the urinary 2/16 estrogen metabolite ratio in human populations, and a report the observed range of normal values in healthy women. Original research studies that included the measurement of urinary estrogen metabolites in human subjects were identified through an extensive Medline search; 43 distinct studies were identified, including a total of 6802 healthy women. The range of mean values of the 2/16 ratio measured with the ELISA method varied from 0.98 to 1.74; in studies of pre-menopausal women the range of mean values was 1.5-2.74, in studies of post-menopausal women mean values ranged from 1.15 to 2.25. The heterogeneity across studies was highly significant (p-value Q-test: <0.0001). In multivariable analyses, only race confirmed its role as an independent predictor of 2/16 ratio (F-value: 7.95; p-value: 0.009), after adjustment for age and menopausal status. There appears to be a large body of data on the 2/16 urinary ratio in healthy women. However, summary estimates are difficult to perform due to the high variability of the published study-specific values. The data suggests that race may be a contributor to 2/16 urinary ratio levels.

Hormone therapy in postmenopausal women affects hemispheric asymmetries in fine motor coordination

Evidence exists that the functional differences between the left and right cerebral hemispheres are affected by age. One prominent hypothesis proposes that frontal activity during cognitive task performance tends to be less lateralized in older than in younger adults, a pattern that has also been reported for motor functioning. Moreover, functional cerebral asymmetries (FCAs) have been shown to be affected by sex hormonal manipulations via hormone therapy (HT) in older women. Here, we investigate whether FCAs in fine motor coordination, as reflected by manual asymmetries (MAs), are susceptible to HT in older women. Therefore, sixty-two postmenopausal women who received hormone therapy either with estrogen (E) alone (n=15), an E-gestagen combination (n=21) or without HT (control group, n=26) were tested. Saliva levels of free estradiol and progesterone (P) were analyzed using chemiluminescence assays. MAs were measured with a finger tapping paradigm consisting of two different tapping conditions. As expected, postmenopausal controls without HT showed reduced MAs in simple (repetitive) finger tapping. In a more demanding sequential condition involving four fingers, however, they revealed enhanced MAs in favour of the dominant hand. This finding suggests an insufficient recruitment of critical motor brain areas (especially when the nondominant hand is used), probably as a result of age-related changes in corticocortical connectivity between motor areas. In contrast, both HT groups revealed reduced MAs in sequential finger tapping but an asymmetrical tapping performance related to estradiol levels in simple finger tapping. A similar pattern has previously been found in younger participants. The results suggest that, HT, and E exposure in particular, exerts positive effects on the motor system thereby counteracting an age-related reorganization.

The effects of α-zearalanol and estradiol benzoate on expression of c-myc, c-fos and epidermal growth factor receptor mRNAs in breast tissues implanted into nude mice

This study was designed to evaluate the effects of a novel phytoestrogen, α-zearalanol (α-ZAL), and estradiol benzoate (B-E₂), on c-myc, c-fos, and EGFR expression in normal human breast tissues implanted into nude mice. A xenograft-model, pieces of normal human breast tissue implanted subcutaneously into 9-10-week-old athymic nude mice, was established. The mice were divided into five groups subjected to the following treatments: normal saline (Controls); α-ZAL at 1 and 5 mg/kg; and estradiol benzoate (B-E₂) at 1 and 5 mg/kg. Treatment was given every other day, and human breast tissues were removed for experiments after treatment for 30 days. The expression of c-myc, c-fos, and EGFR mRNAs were determined by in situ hybridization. α-ZAL decreased expression of c-myc (p < 0.05). About 1 mg/kg α-ZAL increased EGFR expression (p < 0.05) and two dosage of α-ZAL increased c-fos expression (p < 0.01) compared with control. B-E₂ significantly increased expression of c-myc, c-fos, and EGFR mRNAs expression compared with controls (p < 0.01). The extents of the increases in EGFRmRNA expression induced by α-ZAL and in c-fos mRNA by 5 mg/kg α-ZAL were lower than those induced by B-E₂ (p < 0.01). These data suggest that the phytoestrogen α-ZAL may be safer than estrogen on breast.

Are estradiol metabolites involved in gynaecological carcinogenesis?

Certain estradiol metabolites are biologically active, sometimes several times more potent than their parent substance. Highly sophisticated laboratory methods allow us to understand oestrogenic effects as a net effect of the corresponding metabolite pattern. Currently, research is focused on the anticancerogenic effects of 2-hydroxyestrone and particularly 2-methoxyestradiol, as well as the possible carcinogenic properties of 4-hydroxyoestrogens and 16α-hydroxyestrone. The clinical relevance of these activities, demonstrated in in-vitro and animal experiments, remains unclear - it is proven, however, that the metabolite production can be altered in certain malignancies such as endometrial-, breast- and cervical carcinoma. Clinical studies, including our studies, have demonstrated a negative correlation between the ratio of 2-hydroxyestrone to 16α-hydroxyestrone and breast cancer risk. However, the design and interpretation of such studies should consider factors influencing metabolic pattern such as diet, physical activity, smoking, as well as internal diseases and certain drugs.

Estrogen therapy affects right hemisphere functioning in postmenopausal women

It has been suggested that hormone therapy (HT) in postmenopausal women differentially affects verbal and visuo-spatial abilities which mainly rely on left hemisphere (LH) and right hemisphere (RH) functioning, respectively. Thus, it seems likely that HT-related effects on cognition are driven by associated hormonal changes and their impact on functional brain organization, and functional cerebral asymmetries (FCAs) in particular. The present study investigated HT-related effects on FCAs in sixty-seven postmenopausal women who received hormone therapy either with estrogen (E) alone (n=14), an E-gestagen combination (n=22) or without HT (control group, n=31). Saliva levels of free E and progesterone (P) were analyzed using chemiluminescence assays. FCAs were measured with the visual half-field (VHF) technique using a word matching and a figural comparison task. In agreement with previous results, a postmenopausal control group showed a left hemisphere (LH) advantage in the verbal task and a right hemisphere (RH) advantage in visuo-spatial processing. In contrast, both HT groups revealed significantly reduced FCAs in the figural comparison task as a result of an E-related decrease in RH performance. The findings suggest that E-therapy in postmenopausal women can affect visuo-spatial abilities by modulating the functional brain organization and RH functioning in particular.

Breast cancer: Are oestrogen metabolites carcinogenic?

The World Health Organization (WHO) classified oestrogens as carcinogenic in humans. One of the main arguments has been that oestrogens not only can promote cancers but also may initiate mutations caused by certain oestrogen metabolites. Indeed there is evidence that they can have biological properties even at very low concentrations which can exceed manifold those of their parent substance. Highly sophisticated laboratory methods will allow us to understand oestrogenic effects as a net effect of the corresponding metabolite pattern. Current research focuses on the possible carcinogenic properties of 4-hydroxyoestrogens and 16-alpha-hydroxyoestrone, but also on the anticancerogenic effects particularly of 2-methoxyoestradiol. Thus, potential toxic secondary metabolites like 4-quinones can be eliminated, e.g. by methylation. 2-methoxyoestradiol is a potent antiproliferative and antiangiogenic metabolite, and is currently tested in patients with refractory metastatic breast cancer. Observational trials have demonstrated that the ratio of 2- to 16-alpha-hydroxyoestrone is decreased in women with breast cancer. We have been able to demonstrate that oestradiol metabolism during HRT can be influenced by administration route, possibly also by certain progestogens. In in vitro and animal experiments certain oestrogen metabolites indeed can act as carcinogens. However, since for the formation of these metabolites the appearance of very special conditions is a prerequisite and also various protective mechanisms are present, this might only contribute to breast carcinogenesis in very rare cases. However, the clinical relevance remains unclear and it appears to be important to ascertain this issue.

Estradiol gel

OBJECTIVE

To review the pharmacology, pharmacokinetics, safety, and efficacy of a gel containing estradiol that is applied to the skin.

DESIGN

MEDLINE and EMBASE searches were conducted from 1966 to March 2005. Additional references were identified from bibliographies from selected studies in addition to approved product information.

RESULTS

Estradiol gel is indicated for the relief of moderate to severe vasomotor symptoms in menopausal women, and moderate to severe symptoms of vulvar and vaginal atrophy. Women who are intolerant of the oral route, have had previous hypersensitivity skin reactions, or have had difficulties with adhesive patches are ideal candidates for estradiol gel.

CONCLUSIONS

Estradiol gel can effectively reduce menopause symptoms with minimal side effects. Long-term safety data of estradiol gel are required.

Urinary hydroxyestrogens and breast cancer risk among postmenopausal women: a prospective study

BACKGROUND

It has been suggested that a low level of the 2-hydroxyestrogen metabolites (2-OHE) and a high level of 16alpha-hydroxyestrone (16alpha-OHE1) are associated with an enhanced risk of breast cancer. We examined the association between the metabolite levels and breast cancer in a nested case-control study, which also addressed hormone replacement therapy (HRT) and estrogen receptor status of the tumors.

METHODS

24,697 postmenopausal Danish women were enrolled in the "Diet, Cancer and Health" cohort. During follow-up, 426 breast cancer cases were identified and controls were matched by age at diagnosis, baseline age, and HRT use. The concentrations of 2-OHE and 16alpha-OHE1 in spot urine were measured by an enzyme immunoassay. Incidence rate ratios (IRR) and 95% confidence intervals (95% CI) were estimated for total and estrogen receptor-specific breast cancer and were stratified according to HRT use.

RESULTS

A higher incidence of estrogen receptor-positive breast cancer with an enhanced 2-OHE level was observed among current HRT users, IRR per doubling = 1.30 (95% CI, 1.02-1.66), whereas no association was seen among nonusers of HRT, IRR per doubling = 1.00 (95% CI, 0.69-1.45). The association between estrogen receptor-positive breast cancer and the 16alpha-OHE1 metabolite level was in the opposite direction but slightly weaker and statistically insignificant. For estrogen receptor-negative breast cancer, no significant associations were seen.

CONCLUSIONS

The risk of breast cancer, in particular the estrogen receptor-positive type, was enhanced among postmenopausal women using estradiol-based HRT and among those who had a high 2-OHE concentration.

Breast cancer risk during HRT: influence of estradiol metabolites on breast cancer and endothelial cell proliferation

OBJECTIVES

Long-term hormone replacement therapy is associated with an increased breast cancer risk. Evidence is accumulating that estradiol metabolites are involved in carcinogenesis. These metabolites may have proliferating and anti-proliferative properties. We have investigated the effect of 14 metabolites on the proliferation of human breast cancer cells and on the proliferation of human vascular endothelial cells.

METHODS

As cell model, human umbilical vein endothelial cells (HUVEC) and the human breast cancer cell line MCF-7 were used. The relationship between dosage and effect was tested over the pharmacological concentration range of 10(-8) to 10(-5) M.

RESULTS

In HUVECs, all of 10 A-ring metabolites tested stimulated the growth of the endothelial cells at the lower concentrations. At the highest concentration, some A-ring metabolites caused significant inhibitions. The D-ring metabolites showed no marked effects compared to the A-ring metabolites. In MCF-7 cells also, nearly all A-ring metabolites demonstrated a biphasic reaction behaviour on cell proliferation. For the D-ring metabolites, this biphasic pattern was only found for 16 alpha-hydroxyestrone, but the inhibitory effect of this metabolite was weak.

CONCLUSION

These results indicate that certain endogenous estradiol metabolites are able to stimulate breast cancer cell proliferation, and others may be suitable for breast cancer treatment when used in high dosages, since they inhibit cancer cell growth as well as neoangiogensis. This may be of special importance for therapy, since some of these metabolites are virtually devoid of any oestrogenic activity.

An update on the antiestrogenic effect of smoking: a literature review with implications for researchers and practitioners

OBJECTIVE

To draw attention to the implications of smoking in the pathogenesis of osteoporosis and for the effectiveness and safety of hormone therapy. DESIGN Summary of own research and a MEDLINE search of English-language literature on the antiestrogenic effect of smoking in pre- and postmenopausal women published during the past two decades.

RESULTS

Numerous observations suggest that part of the detrimental effect of smoking on bone metabolism is mediated by an adverse influence on sex-steroid metabolism, and in particular by an estrogen-lowering effect. Furthermore, in smokers, serum concentrations of estradiol and estrone during oral, but not parenteral, hormone therapy (HT) reach only half the concentrations of nonsmokers. Thus, cigarette smoking may reduce the favorable effects of HT significantly and may even negate the protective effects. In such cases, the failure of preventive therapy is a failure of dosing rather than of HT per se.

CONCLUSIONS

We urge colleagues to take the antiestrogenic effect of smoking into account when drawing conclusions from population-based trials, as well as when prescribing HT to their patients for the prevention of menopause-related health problems.

HPLC determination of estradiol, its degradation product, and preservatives in new topical formulation Estrogel HBF

This paper deals with the development of a novel method for simultaneous determination of estradiol, its degradation product estrone, and two preservatives, methylparaben and propylparaben, in the topical preparation Estradiol HBF. After optimization of the analytical conditions the method was validated and applied in studies of the stability of the topical preparation Estrogel HBF. Separation of all these compounds was performed on a Supelco Discovery C18 (250 mm x 3.0 mm, 5 microm) analytical column. A mixture of acetonitrile, methanol, and water (23:24:53 v/ v) was chosen as mobile phase. UV absorbance at 225 nm was used for detection and quantitation of analytes. The total analysis time was less than 12 min at a flow rate of 0.9 mL min(-1). All the compounds were isolated from the topical gel by simple extraction with an acetonitrile solution of hydrocortisone, as internal standard, and using sonication and centrifugation thereafter. The supernatant was injected directly on to the analytical column. The recovery of the procedure was from 96.9 to 100.4%. Validation of method according international guidelines was successfully performed.