Women’s health: what is the function of estrogen?

Women’s health and women-specific health topics prompt us to ask important questions about a specific gender gap in health. Why do women tend to live longer than men on average? Why do men require more medical care beyond a certain age than women? Amid the current health crisis, it’s just as important as it has ever been to understand the health and well-being of women around the world.

On average, women live five years longer than men. For a long time, researchers believed that the healthier lifestyle of women overall was solely responsible for this. But even in orangutans, whose genetic makeup is similar to ours, women outlive men. Researchers are therefore looking to hormones for answers behind the difference in life expectancy.

One of the most crucial female sex hormones is estrogen. It can protect women from diseases such as osteoporosis, high blood pressure and memory disorders, among others – and may thus contribute to a longer lifespan. Generally speaking, female sex hormones have a stronger grip on us than we think, with hormone imbalances triggering mood swings, irregular menstrual cycles and libido. Once you discover what causes these issues, it can often become clearer how you can remedy your hormone imbalances.

Learn about estrogen deficiency and estrogen dominance, the function of estrogen, and how you can increase your estrogen levels.

What are estrogens?

The word ‘estrogen’ comes from Greek, meaning ‘to produce passion’.^[1] What we refer to as the female sex hormone is actually a collective term for the female hormones oestradiol, oestrone and oestriol. The most important of these, oestradiol, is responsible for the majority of the tasks of the female sex hormones.^[2] It often works together with another hormone, progesterone.

Did you know that progesterone is the precursor of many hormones – for example, testosterone and estrogen. It is particularly important for pregnant women, as it builds up the lining of the uterus and promotes a healthy pregnancy.^[2]  

Put simply, our body produces the two sex hormones estrogen and testosterone for a single reason: for reproduction. If the level of one of the hormones decreases, the desire for sexual intercourse also decreases.^[2]

What is the function of estrogen?

Estrogen turns girls into sexually mature women. While still in the womb, the vagina and ovaries are formed, and during puberty, the hormone ensures breast growth and makes women fertile. In addition, the hormone is involved in other noticeable changes:^[2]

• Formation of underarm and pubic hair
• Lactic acid production in the vagina
• Texture and shine of the skin
• Development of fat in certain areas of the body (hips/buttocks)
• Increase in sex drive/libido

Function of estrogen in women[3, 4]
Skin	Promote water retention in skin/tissue and ensure smooth skin
Blood vessels	Dilate blood vessels and lower blood pressure, protect against heart attack
Nervous system	Lift mood
Sugar metabolism	Affect blood sugar level in a positive way
Lungs	Increase lung function
Bones	Inhibit bone resorption and promote bone formation
Intestine	Strengthen the movement of the intestines and promote good bowel function

Estrogen levels during menstrual cycle phases

Bad moods, powerful emotions or euphoria – that’s how women describe the roller coaster of emotions they experience during their period. Not to mention the pain and the intensity of menstruation. Behind these symptoms are highly complex processes that take place in the uterus. The culprits behind these symptoms are both estrogen and progesterone.

Every 21 to 35 days, the female body goes through various menstrual cycle phases that end or begin with menstruation. In a cycle of 28 days, the phases run approximately like this:^[2]

Day 1 to 4: Menstrual bleeding lasts two to six days.

Day 5 to 14: Menstruation begins and ends at the time of ovulation; the endometrium builds up with about 20 follicles, only one of which produces estrogen, and in large quantities.

Day 14: With ovulation, estrogen levels reach their peak. During this phase, women feel most comfortable and have a higher interest in sexual intercourse. Morning body temperature rises by 0.5 degrees by the end of the cycle. Here, women are particularly fertile because the cervix opens and sperm can penetrate it.

Day 15 to 28: While estrogen production decreases, progesterone production increases. Progesterone levels peak one week before the onset of the period. Symptoms during this phase are usually unpleasant, with breast tenderness, weight gain, water retention, irritability, tearfulness and decreased sexual desire.

If the egg is not fertilised, progesterone and estrogen levels drop, and the uterine lining is shed. This is when menstruation begins. If the egg is fertilised, progesterone levels continue to rise in preparation for a possible pregnancy.

What does the pill do to your body?

The contraceptive pill, often simply called ‘the pill’, has been available in the United Kingdom since 1967^[5]; before its widespread legalisation, the pill was only available to married women. The pill is in fact described as one of the most significant advances made in science and gender equality in the twentieth century.

Around 3.1 million women in the United Kingdom take either the mini-pill or the combined pill.^[5] As a rule, the pill contains two hormones, estrogen and progestogen. They prevent ovulation as well as fertilisation in the uterus by:^[7]

• inhibiting the formation of messenger substances in the brain that are normally required for ovulation;
• altering the mucus in the cervix, so that sperm cannot travel through it;
• altering the lining of the uterus, so that the egg cannot be fertilised

An estrogen-free pill, also called a mini-pill, consists only of progestogen. The hormone does not normally stop ovulation. By changing the mucus in the cervix, progestogen prevents pregnancy.^[6]

Did you know that, according to the guidelines of the German Society of Gynecology and Obstetrics, the risk of cardiovascular disease increases 20- to 87-fold if smokers take a pill containing estrogen.^[8]

What happens to estrogen in menopause?

During menopause, the body no longer produces eggs, and the ovaries gradually stop working. The production of progesterone and estrogen gradually decreases and menopause symptoms may include hot flushes, palpitations and sleep disturbances:^{[3, 9]}

Menopause symptoms due to estrogen deficiency	Number of women experiencing menopause symptoms moderately or strongly
Joint and muscle complaints	49%
Sleeping disorders	44%
Depressive moods	40%
Decrease in libido	40%
Reduced performance and memory	37%
Hot flushes	33%
Vaginal dryness	25%
Urinary tract complaints	16%
Heart trouble	16%

Did you know that, on average, women reach menopause between the ages of 45 and 55 years of age; for smokers, it occurs two years earlier on average.^[3]

What is estrogen deficiency?

Estrogen deficiency can occur at different phases of a woman’s life. The lowest estrogen levels are produced during menstruation. During menopause, estrogen production stops almost completely and the body’s estrogen levels decrease continuously over the years.

Are my estrogen levels normal?

You can determine your estrogen levels with a saliva test, for example. To find out if your level is within the normal range, you need to know which phase of your cycle you were in at the time the test was taken. The concentration of the hormone will also change depending on this factor:

Stage in cycle	Reference range (in picograms per millilitre)
From the first day after menstruation	1.29–7.76 pg/ml
Ovulation	3.79–16.05 pg/ml
Time between ovulation and menstruation (luteal phase)	1.22–8.43 pg/ml
During menopause	0.56–4.39 pg/ml
Reference value for men	less than 2.50 pg/ml

Please do not measure your estrogen levels while you are on your period!

What are the causes of low estrogen levels?

Naturally, women during menopause experience estrogen deficiency. For women who are not undergoing menopause, a hormonal imbalance or disruption can be a cause. This disruption can result from^[10]

• malnutrition,
• extreme physical activity and
• stress.

In addition, various diseases trigger estrogen deficiency – for example, adrenal insufficiency and procedures such as the surgical removal of one or both ovaries.^[10]

Taking contraceptives, such as the birth control pill, can also cause estrogen deficiency. The synthetic estrogens contained in the drugs suppress the body’s own estrogen production. Although the pills themselves contain estrogens, this is not enough to replace the body’s own production in some people.^[10]

What are typical estrogen deficiency symptoms?

Estrogen deficiency symptoms for women who have not yet reached menopause include the absence of menstrual periods, frequent intermenstrual bleeding and even an unfulfilled desire to have children. Late onset of puberty can also indicate an estrogen deficiency. However, this often has little to do with hormonal problems and is rather due to family history.^[11]

Typical issues and symptoms experienced during menopause include:^[12]

• sweating and hot flushes,
• headaches, restlessness, irritability, depression, insomnia,
• dry skin and mucous membranes (often the vagina),
• hair loss,
• weight gain and
• infertility.

Is estrogen deficiency dangerous?

Due to declining estrogen levels, the hormone can no longer perform its protective tasks adequately. Therefore, the risk of developing arthrosis, arteriosclerosis, osteoporosis, bone fractures and memory disorders increases in women over the age of 50.^[12]

You can read more about preventing osteoporosis in our Health Portal article.

Can menopause cause urinary tract infections?

It is no coincidence that urinary tract infections are more common in menopausal women. An observation by researchers at the Washington University School of Medicine shows that estrogen levels affect the susceptibility of the urinary bladder to infections. The research team studied mice that had their ovaries surgically removed. The number of germs in the urine increased significantly.^[13]

If you are menopausal, you should also make sure you are taking enough vitamin D supplements and calcium to reduce the risk of osteoporosis.^[12]

What happens if a man has low estrogen?

The female hormones estrogen and progesterone are also produced in the male body, but in much smaller quantities. Nevertheless, both hormones carry out important functions in men: estrogen influences body fat composition, bone formation, skin metabolism and libido – it is not only testosterone levels that are responsible for this! Both hormones, estrogen and testosterone, regulate each other.^[12] Progesterone ensures better fertility in men. It activates the processes necessary for the sperm to reach the egg.^[2]

Did you know that studies suggest that men with an estrogen deficiency also have a testosterone deficiency? This is because estrogen is formed from testosterone with the help of enzymes. Read more about the signs of low testosterone levels in our Health Portal article.^[14]

Do men also go through menopause?

Due to a decrease in hormone production in the testicles, men can also have insufficient estrogen in their bodies as they get older. Estrogen deficiency symptoms in men are often physical changes, such as an increase in fat mass and a lower libido. Estrogen dominance is also possible in men. This can be due to various reasons, for example severe obesity.^[15]

Is there a link between estrogen deficiency and weight gain?

In 2013, researchers tested what happens in the male body when there is an artificially induced lack of estrogen. The 400 healthy men aged 20 to 50 showed an increase in fat mass, but there was no effect on muscle mass. According to the findings of the study, a lack of estrogen leads to weight gain.^[16]

As women get older, they often notice how the fat from the hip area moves to the stomach. This is due to female hormones. Previously, fat shifted to the hips and buttocks as much as possible, so that nothing would stand in the way of pregnancy. In addition, the estrogen made it easier to burn the fat. At an older age, the fat deposits are much more stubborn.^[17]

Although body fat distribution is essentially hormonal, diet may also play a role: according to one study, waist circumference increased with sausage and meat consumption, but not with fruit and vegetable intake. Menopausal women should therefore pay special attention to their diet.^[17]

How do I increase my estrogen levels?

If your estrogen levels are too low, the first thing to do is to find the cause. If you know why you have an estrogen deficiency, you can start figuring out which treatment is best for you. Which treatment is suitable – and, above all, effective – and health risks must be considered, depends on the reason behind estrogen deficiency. The following treatment options are common:^[18]

• Phytoestrogens
• Caffeine
• Hormone replacement therapy

What are the side effects of phytoestrogen?

Phytoestrogens are so-called plant estrogens with opposite properties. They have a similar effect to the female sex hormone because they mimic its effect – only in a weakened form. But note that phytoestrogens can also have an anti-estrogenic effect and inhibit the body’s own estrogen production.^{[19, 20]}

One study found that high levels of phytoestrogens in the blood correlate with a reduced risk of breast cancer. So, it is not yet clear whether phytoestrogens can reduce the risk of cancer; researchers aim to conduct further studies.^[20]

So, before you change your diet to foods containing phytoestrogens, talk to your doctor. Women over 50 usually benefit from such therapy. In younger women, the cause of a deficiency is often due to being underweight, late onset of puberty or high cortisol levels. Phytoestrogens are associated with the risk of estrogen excess in them.

Which foods boast a high phytoestrogen content?

Phytoestrogens can increase estrogen levels in the body. The most important phytoestrogens for the body are the so-called isoflavones and lignans. Men should not regularly consume foods with phytoestrogens in large quantities.^[21]

Isoflavones are contained in:	Lignans are contained in:
Soybeans	Linseed
Miso	Pumpkin seeds
Tofu	Strawberries
Soy milk	Cranberries
Beans	Olives
Peas	Broccoli

The phytoestrogen content decreases from top to bottom.

If you want to avoid genetically modified foods, you should opt for organic alternatives when buying dairy products, eggs and meat. The use of genetically modified soya is banned in the EU. Nevertheless, genetically modified soya enters our diet when we eat milk, eggs and meat from conventional production. This is because meat from animals fed with genetically modified feed does not have to be labelled! Organic products thus represent an alternative to such foods.^[22]

Phytoestrogens can only function in the body when our intestinal germs have metabolised them. The conversion thus depends on whether you have healthy gut flora. You can check your intestinal health by taking a gut microbiome test, which a laboratory then analyses for the right balance of good and bad bacteria in your gut.^[20]

Hormone replacement therapy: how does it work?

In the 1980s, hormone replacement therapy was common, but today, it is highly controversial. In 2002, US researchers from the Women's Health Initiative (WHI) studied 16,000 menopausal women. Half were treated with estrogen and progesterone, the other half were not.^[24]

After five years, the study was stopped early – in the group of hormone users, there was an increase in heart attacks, strokes and thromboses. The number of breast cancer diagnoses also increased. In addition, the effectiveness of estrogen was investigated in women without a uterus. This sub-study was also discontinued after seven years because there were no health benefits, and strokes and thromboses also increased here.^[24]

After the publication of the study, the prescription of hormones decreased by 80 per cent in the same year. Critics, such as the German Society for Endocrinology, emphasise that the study’s results on cancer risks were misinterpreted. Hormone therapy does not generally increase the risk of breast cancer, according to an expert opinion in the New England Journal of Medicine 2016^[25]. It is necessary to take into account age, duration and dosage of hormone therapy, physical activity, weight and genetic factors. The participants of the WHI study were already of advanced age, so the results, according to the critics, do not indicate a risk for women in their 40s and 50s.^{[25, 26]}

Is hormone replacement therapy dangerous?

Recent studies from Denmark and a rewrite of the WHI study with younger participants (aged 50 to 60 years) revealed certain benefits of hormone therapy. Usage during early menopause was effective in treating symptoms and had a positive effect on death rates and the cardiovascular system. The administration of estrogen alone in women without a uterus reduced the risk of breast cancer.^{[27, 28]}

According to a statement by the North American Menopause Society in 2010, estrogen therapy with or without progesterone is the most effective treatment to relieve menopausal symptoms.^[29]

Hormone replacement therapy should never be used for longer than necessary – that is, for a maximum of five years. Further treatment should be discussed with your doctor at least once a year.^[12]

In a nutshell: Current studies and experts emphasise the advantages of hormone replacement therapy. Nevertheless, there is a lack of further long-term studies that rule out risks and specify the duration of safe therapy. An individual weighing of the benefits and risks is important. Age and state of health are important criteria that you should discuss with your doctor or therapist.

What can I take instead of hormone replacement therapy?

As hormone replacement therapy is occasionally associated with risks, alternatives have also been known and recommended for some time.

Is it safe to use estrogen cream?

The administration of estrogen via gels, patches or creams is still rare. Estrogen absorption through the skin means that the liver is less stressed. Another advantage is that the dose is lower, it can be used individually, and it is much less risky for smokers and overweight people.^[12]

Creams containing estrogen are usually used for symptoms affecting the urinary and genital organs (e.g. vaginal dryness).^[30]

How effective are natural alternatives to hormone therapy?

Just how effective herbal alternatives with estrogen-like effects are – such as monk’s pepper, black cohosh and lady’s mantle – has not yet been completely clarified scientifically. However, it is clear that they can be effective. The following are frequently recommended:^[31]

Phytoestrogen	Effect/Use
Monk’s pepper	Regulates cycles; treats breast tenderness, sensitivity to touch, spotting, bleeding between periods
Soy products	Counteracts bone decalcification
Black cohosh1	Promotes an estrogen-like effect; treats hot flushes, sleep disturbances, changes in the skin and mucous membranes
Lady’s mantle	Treats hot flushes and sweats
Sage	Treats hot flushes with sweating
Valerian	Treats nervousness, concentration problems, difficulty falling asleep
Hops	Treats anxious restlessness and sleep disturbances
St. John’s wort2	Treats depression, mood swings

¹ Black cohosh preparations should always be taken under a doctor’s medical supervision because it is not clear whether there is a risk of liver damage with long-term intake (longer than three months).

² Caution: St. John’s wort increases sensitivity to the sun; it can impair the effectiveness of other medicines (hormone preparations, such as the pill).

Herbal remedies in concentrated form (in tablets, powder, drops or dragées) have not yet been sufficiently researched and may have undesirable side effects. You can safely use the herbal alternatives as teas and in herbal form.^[31]

Can acupuncture help with hormones?

Acupuncture is an alternative Chinese medicine technique that dates back to around 2 BC and involves inserting solid needles into acupoints in the surface of the skin.^[38] Such a method is often used for various conditions, such as headaches, tennis elbow, arthritis, strokes and morning sickness. The first European countries to adopt this ancient technique were France and Germany.

An increasing number of studies have indicated that acupuncture could also play some role in addressing hormonal imbalances and relieving menopause symptoms. A study conducted by BMJ revealed that acupuncture drastically decreased the occurrence of hot flushes, sleeping problems, emotional symptoms and skin and hair problems in menopausal women.^[36]

Although more studies need to be carried out, accredited medical associations, such as AACP (the Acupuncture Association of Chartered Physiotherapists) and WHO have deemed acupuncture a suitable treatment for women’s health and hormonal imbalances.^[37]

What about estrogen dominance and progesterone deficiency?

Causes of estrogen dominance (also called estrogen surplus) can be high estrogen intake, obesity, stress, poor nutrition and poor estrogen metabolism.^{[32, 33]}

High estrogen levels become noticeable through symptoms such as heavy menstrual bleeding with pain, pronounced mood swings and cysts. Estrogen dominance can begin in our mid 30s, but it usually only becomes a problem at the beginning of menopause.^[33]

Why is belly fat so dangerous?

Fat cells produce estrogen. The more fat we have, especially belly fat, the more estrogen is released. This causes estrogen dominance, especially in men who are heavily overweight. This is why men and women who are overweight should keep an eye on their estrogen levels.^{[32, 33]}

Are there too many hormones in your diet?

Furthermore, to prevent or correct poor estrogen metabolism, the liver must be healthy. A healthy liver helps your body to reduce high estrogen levels. Avoid factors that can put extra stress and strain on your liver, such as:^{[32, 33]}

• A lot of sugar and alcohol
• Environmental toxins, such as hormones in plastic bottles
• Obesity
• Large amounts of animal products

‘The dose makes the poison’ – this principle also applies hormones in our diet. Those who eat too many dairy and meat products from conventional production ingest a lot of hormones in an unnatural way. This is because in conventional farming, hormones are administered to animals to make them grow faster. Organic products are an alternative – or you eat less animal products in general. 

We also ingest hormones via plastic bottles, plastic film and food in plastic containers. You can avoid these too by using a reusable glass water bottle and glass containers for food you prepare in the microwave.^{[32, 33]}

Is caffeine bad for hormones?

A study in the American Journal of Clinical Nutrition has documented the previously unknown effect of caffeine on the female hormone balance. Caffeine, depending on origin, can indeed lead to high estrogen levels – but not in every woman. Two cups of coffee a day increased estrogen levels in Asian and African–American women. In US participants, however, coffee had the opposite effect. Other caffeinated drinks, including green tea, increased estrogen levels in all women. The reasons behind this are unclear.^[23]

What does stress do to hormones?

If you are stressed for a long time, your progesterone levels will drop. Avoid this by ensuring you take time out every day to relax and promoting mental balance. Make sure you get seven to eight hours of sleep every night. Relaxation techniques such as yoga, meditation and autogenic training can also help reduce stress.^{[32, 33]}

To discover more about techniques to cope with stress and to find out more about emotional resilience and stress, head over to our blog article. 

How do you check estrogen levels?

There are various ways to detect low or high estrogen levels. These include urine, saliva and blood tests. Only doctors are allowed to make a definite diagnosis of estrogen deficiency or estrogen dominance.

An estrogen test, for example, will give you an indication of your current hormone levels. In addition to the free, active estrogen (oestradiol), your progesterone levels are also measured in a saliva sample. Since the hormones in the body are cycle-dependent, you need to know which cycle phase you are in when you take the sample. Of course, this only applies to women. For men, there is a single reference value.

Why should estrogen levels in saliva be tested?

Estrogen and progesterone measured in the blood is protein-bound – that is, inactive. A blood sample analysis, in this case, therefore only shows approximate values. The active form can only be measured in saliva. Studies show that the blood values after hormone intake are often in the normal range, while significant increases can be measured in the saliva.^{[34, 35]}

Please note that there are factors that can have an influence on your test results. See the list of medications that influence your estrogen levels before taking the test.

The function of estrogen – at a glance

What is estrogen?

The female sex hormones oestradiol, oestrone and oestriol are collectively called estrogens. Estrogens form the female sex organs. Together with the hormone progesterone, they control the female cycle. The production of estrogens fluctuates accordingly with the menstrual cycle; it is at its highest approximately two weeks before the onset of menstruation.

Why is estrogen in the pill?

The contraceptive pill contains artificial estrogens and progestogens that prevent the usual hormonal fluctuations. This prevents eggs from growing in the ovaries and implanting in the uterus. For pregnancy to occur, the eggs would have to be fertilised in the uterus. The mini-pill works without estrogen.

What is estrogen deficiency?

Estrogen deficiency usually sets in with increasing age in both women and men – in women, it is a side effect of menopause. Low estrogen levels then lead to mood swings, hot flushes and weight gain, among other things. It also increases the risk of diseases such as arthrosis, arteriosclerosis and osteoporosis.

How do I increase my estrogen levels?

Phytoestrogens – that is, estrogens contained in plants, can increase estrogen levels. They are found in foods like soy, flaxseed and beans. Other treatment options include hormone replacement therapy and alternative hormone therapies.

What is estrogen dominance?

With estrogen dominance (excess estrogen), there is too much estrogen and too little progesterone in the body. Possible causes are stress, poor estrogen metabolism and especially obesity, in addition to an increased estrogen intake.

How do you check estrogen levels?

The levels of estrogen and progesterone in the body can be measured with a saliva sample. Women need to take into account which phase of their cycle they are in when taking the hormone test, as hormone levels fluctuate significantly.

Sources

^[1]        Gerabek, W. E., Haage, B. D., Keil, G., Wegner, W. Enzyklopädie Medizingeschichte. Berlin: de Gruyter, 2005.

^[2]        Silbernagl, S., Despopoulos, A., Gray, R., Rothenburger, A. Taschenatlas Physiologie, 8., revised and extended edition. Stuttgart New York: Thieme, 2012.

^[3]        ‘Dr. Mareike Groeneveld, Dr. Lioba Hofmann. Die Wechseljahre der Frau - Ernährung und andere Lebensstilfaktoren. Bundeszentrum für Ernährung’, available at: https://www.bzfe.de/_data/files/eif_2011_10__wechseljahre_frau.pdf, accessed on 13 Aug. 2018 [online].

^[4]        ‘Wechseljahresbeschwerden / klimakterische Beschwerden’, Frauenärzte im Netz, available at https://www.frauenaerzte-im-netz.de/koerper-sexualitaet/wechseljahre-klimakterium/wechseljahresbeschwerden-klimakterische-beschwerden/#c329, accessed on 14 Aug. 2018 [online].

^[5]      Bridge, S. ‘A history of the pill’ the Guardian, Sep. 2007, available at https://www.theguardian.com/society/2007/sep/12/health.medicineandhealth#:~:text=It%20was%20introduced%20in%20the,by%20around%20100%20million%20women, accessed on 25 Feb. 2021 [online].

^[6]       Wiegratz, I. Thaler, C. J. ‘Hormonal Contraception – What Kind, When, and for Whom?’, Deutsches Aerzteblatt Online, vol. 108(28–29), 495–506, July 2011, doi: 10.3238/arztebl.2011.0495.

^[7]        ‘Wie wirkt die Antibabypille? | Die Techniker’. https://www.tk.de/techniker/service/gesundheit-und-medizin/schwangerschaft-und-geburt/wie-wirkt-die-antibabypille-2013536, accessed on 13 Aug. 2018 [online].

^[8]        ‘Deutsche Gesellschaft für Gynäkologie und Geburtshilfe e.V.: Leitlinien, Empfehlungen, Stellungnahmen Stand September 2010’, available at: https://www.dggg.de/fileadmin/documents/leitlinien/archiviert/federfuehrend/015015_Empf%C3%A4ngnisverhuetung/015015_2010.pdf, accessed on 13 Aug. 2018 [online].

^[9]        Schultz-Zehden, B. ‘Körpererleben im Klimakterium’, Journal für Menopause, vol. 5(1), 10, 1998.

^[10]      Jagfeld, E. P., Heuschkel, B. C., Frauenheilkunde natürlich Das Fachbuch für die Praxis. Norderstedt: Books on Demand, 2011.

^[11]      Classen, M., Diehl, V., Schmiegel, W., Innere Medizin, 6th Edition, Urban & Fischer Verlag/Elsevier GmbH, 2009.

^[12]      Römmler, A.,Hormone: Leitfaden für die Anti-Aging-Sprechstunde; [Gestagene, Orthomolekulare Medizin, Wachstumshormone, Testosteron, Melatonin, Progesteron, Östrogen, Dehydroepiandrosteron, Chronobiologie, Serotonin, Pregnenolon]. Stuttgart: Thieme, 2014.

^[13]      Wang, C., Symington, J. W., Ma, E., Cao, B., Mysorekar, I. U. ‘Estrogenic Modulation of Uropathogenic Escherichia coli Infection Pathogenesis in a Murine Menopause Model’, Infection and Immunity, vol. 81(3), 733–739, March 2013, doi: 10.1128/IAI.01234-12.

^[14]      ‘Östrogenmangel macht Männer dicker’, Deutsches Ärzteblatt, 12. Sep. 2013, available at https://www.aerzteblatt.de/nachrichten/55823/Oestrogenmangel-macht-Maenner-dicker, accessed on 15 Aug. 2018 [online].

^[15]      Leifke E., Gorenoi, V., Wichers, C., Von Zur Mühlen, A., Von Büren, E., Brabant, G. ‘Age-related changes of serum sex hormones, insulin-like growth factor-1 and sex-hormone binding globulin levels in men: cross-sectional data from a healthy male cohort’, Clin. Endocrinol. (Oxf), vol. 53(6), 689–695, Dec. 2000, doi: 10.1046/j.1365-2265.2000.01159.

^[16]      Finkelstein, J. S. et al., ‘Gonadal Steroids and Body Composition, Strength, and Sexual Function in Men’, New England Journal of Medicine, vol. 369(11), 1011–1022, Sep. 2013, doi: 10.1056/NEJMoa1206168.

^[17]     ‘Ernährung in den Wechseljahren’ Ernährungs Umschau, 28 May 2008, available at: https://www.ernaehrungs-umschau.de/news/28-05-2008-ernaehrung-in-den-wechseljahren/, accessed on 15 Aug. 2018 [online].

^[18]      Kleine-Gunk, B. Das Frauen-Hormone-Buch, 2., revised, Stuttgart: TRIAS, 2013.

^[19]      Kulling, S., Watzl, B, ‘Phytoöstrogene’, Ernährungs Umschau, 16 June 2003, available at https://www.ernaehrungs-umschau.de/print-artikel/16-06-2003-phytooestrogene/, accessed on 17 Aug. 2018 [online].

^[20]      Danz, A. ‘Gut durch die Wechseljahre’, UGBforum spezial, 20–22, 2015.

^[21]      ‘USDA Database for the Isoflavone Content of Selected Foods, Release 2.0’, p. 69, 

^[22]      ‘WWF Deutschland. Sojaboom in deutschen Ställen. 2012.’, available at: https://www.wwf.de/fileadmin/fm-wwf/Publikationen-PDF/WWF-Studie_Sojaboom_in_deutschen_Staellen.pdf, accessed on Aug. 20, 2018. [online].

^[23]      Schliep, K. C. et al., ‘Caffeinated beverage intake and reproductive hormones among premenopausal women in the BioCycle Study’, The American Journal of Clinical Nutrition, vol. 95(2), 488–497, Feb. 2012, doi: 10.3945/ajcn.111.021287.

^[24]      ‘Women’s Health Initiative (WHI) | National Heart, Lung, and Blood Institute (NHLBI)’, available at https://www.nhlbi.nih.gov/science/womens-health-initiative-whi, accessed on Aug. 16, 2018 [online].

^[25]      Manson, J. E., Kaunitz, A. M. ‘Menopause Management — Getting Clinical Care Back on Track’, New England Journal of Medicine, vol. 374(9), 803–806, March 2016, doi: 10.1056/NEJMp1514242.

^[26]      ‘Hormontherapie: Endokrinologen fordern Trendwende bei...’, D. Ä. G. Ärzteblatt Redaktion Deutsches, 31 Aug. 2017, available at https://www.aerzteblatt.de/nachrichten/77830/Hormontherapie-Endokrinologen-fordern-Trendwende-bei-Wechseljahresbeschwerden, accessed on 16 Aug. 2018 [online].

^[27]      Sarrel, P. M., Njike, V. Y., Vinante, V., Katz, D. L. ‘The Mortality Toll of Estrogen Avoidance: An Analysis of Excess Deaths Among Hysterectomized Women Aged 50 to 59 Years’, American Journal of Public Health, vol. 103(9), 1583–1588, Sep. 2013, doi: 10.2105/AJPH.2013.301295.

^[28]      Schierbeck, L. L. et al., ‘Effect of hormone replacement therapy on cardiovascular events in recently postmenopausal women: randomised trial’, BMJ, vol. 345(oct09 2), e6409–e6409, Oct. 2012, doi: 10.1136/bmj.e6409.

^[29]      ‘Estrogen and progestogen use in postmenopausal women: 2010 position statement of The North American Menopause Society’, Menopause, vol. 17(2), 242–255, March 2010, doi: 10.1097/gme.0b013e3181d0f6b9.

^[30]      ‘Therapie von Beschwerden in den Wechseljahren’,D. Ä. G. Ärzteblatt Redaktion Deutsches, 27 Apr. 2012, available at https://www.aerzteblatt.de/archiv/125120/Therapie-von-Beschwerden-in-den-Wechseljahren, accessed on 17 Aug. 2018 [online].

^[31]      ‘Wechseljahre’, pro familia, available at https://www.profamilia.de/themen/sexualitaet-und-aelterwerden/wechseljahre.html, accessed on 16 Aug. 2018 [online].

^[32]      ‘Don’t Let Your Estrogen Dominate You!’, K. A. B. Foundation, available at http://keep-a-breast.org/dont-let-your-estrogen-dominate-you/, accessed on 20 Aug. 2018 [online].

^[33]      Marbach, E. Östrogen-Dominanz: die wahre Ursache für PMS und Wechseljahrsbeschwerden, original edition, Breisach: Marbach, 2009.

^[34]      O’Leary, P., Feddema, P., Chan, K., Taranto, M., Smith, M., Evans, S.‘Salivary, but not serum or urinary levels of progesterone are elevated after topical application of progesterone cream to pre-and postmenopausal women’, Clin. Endocrinol. (Oxf), vol. 53(5), 615–620, Nov. 2000, doi: 10.1046/j.1365-2265.2000.01130.

^[35]      Stanczyk, F. Z., Paulson, R. J., Roy, S. ‘Percutaneous administration of progesterone: blood levels and endometrial protection’, Menopause, vol. 12(2), 232–237, March 2005, doi: 10.1097/00042192-200512020-00019.

^[36]      Lund, K. S., Siersma, V., Brodersen, J. et al. ‘Efficacy of a standardised acupuncture approach for women with bothersome menopausal symptoms: a pragmatic randomised study in primary care (the ACOM study)’, BMJ Open, vol. 9(1), e023637, 2019, doi: 10.1136/bmjopen-2018-023637.

^[37]      Roberts, J., Moore, D ‘Mapping the evidence base and use of acupuncture within the NHS’, Department of Public Health and Epidemiology West Midlands Health Technology Assessment Group, The University of Birmingham, September 2006, available at https://www.birmingham.ac.uk/Documents/college-mds/haps/projects/WMHTAC/REPreports/2006/MappingAcupunture.pdf, accessed on 25 Feb. 2021 [online].

^[38]      Ma, K. W. ‘Acupuncture: Its place in the History of Chinese Medicine’. Acupuncture in Medicine, vol. 18(2), 2000; 88-99, doi:10.1136/aim.18.2.88.

^[39]      ‘Overview: Menopause’ NHS, 29 Aug. 2018, available at https://www.nhs.uk/conditions/menopause/, accessed on 24 Feb. 2021[online].

^[40]      ‘Women’s health’ World Health Organization, available at https://www.who.int/health-topics/women-s-health/, accessed on 24 Feb. 2021 [online].

^[41]      Yuanqing, P. et al. ‘Acupuncture for Hormone Therapy–Related Side Effects in Breast Cancer Patients: A GRADE-Assessed Systematic Review and Updated Meta-Analysis.’, Integrative Cancer Therapies, vol. 19, Jan 2020, doi:10.1177/1534735420940394.

^[42]      Boeschen, D., Günther, J., Chytrek, D., Schoch, G.-G., Glaeske, G.‘Pillenreport - Ein Statusbericht zu oralen Kontrazeptiva’, p. 63.  

^[43]      ‘Acupuncture: Review and Analysis of Reports on Controlled Clinical Trials’, World Health Organization, available at https://www.acupuncture.org.uk/index.php?option=com_k2&id=2205_6f7d26dda5bb479cdd92415b01095c4b&lang=en&task=download&view=item, accessed on 25 February 2021 [online].