What is it and what do I need to know?

What is oestrogen?

Oestrogen (or estrogen) is one of the main female sex hormones, but it plays a key role in both the male and female body. As well as regulating puberty and the female reproductive system, it also helps to strengthen bones and prevent atherosclerosis (plaque build-up in arteries).

It is produced by your hormonal (endocrine) system and moves through the bloodstream.

How does it affect our bodies?

In the female body, estrogen is needed for:

  • Puberty
  • The menstrual cycle
  • Pregnancy
  • Bone strength
  • Cardiovascular vasculo-protective action (reduces blood clotting)
  • Maintaining normal cholesterol levels
  • Weight gain

What are the side effects of having an imbalance in estrogen levels?

Having too much or too little oestrogen can affect the way in which the body functions and can contribute to the development of chronic conditions such as breast cancer, endometriosis and infertility. For women, low oestrogen can lead to menopausal symptoms, such as trouble sleeping, headaches, decreased libido, irregular periods, mood swings and hot flushes. Too much oestrogen can actually have a similar effect: irregular periods, fatigue, decreased libido, mood disorders, severe premenstrual pain, cysts and weight gain.

Causes of excess oestrogen can include puberty changes, obesity, diabetes, pregnancy, ovarian or adrenal gland tumors, medications and high blood pressure.

In the male body, estrogen is needed for:

  • Sexual development
  • Sexual function (modulating libido, erectile function, and spermatogenesis)
  • Weight gain

What are the side effects of an imbalance in oestrogen levels for men?

  • Low libido, decreased morning erections, decreased erectile functions
  • Weight gain around waist
  • Enlarged breast tissue
  • Increased abdominal fat
  • Feeling tired
  • Loss of muscle mass
  • Emotional disturbances
  • Type 2 diabetes
  • Lower urinary tract symptoms associated with prostatic hyperplasia

Men tend to be more concerned about their testosterone levels, especially as they age beyond 40 and testosterone starts to decline naturally. High levels of testosterone can also be a cause for concern when it comes to prostate cancer and can require hormone therapy.

A proper balance between oestrogen and testosterone is key for good prostate and heart health and for maintaining strong, healthy bones. It also affects your brain, heart and skin.

In men, too much oestrogen has been linked to an increased risk of strokes, coronary heart disease, enlarged prostate and prostate cancer, low libido and weight gain. It may also cause the development of excessive breast tissue, erectile dysfunction, decreased libido, mood disorders and fatigue. Low oestrogen levels can cause low libido and weight gain around waist.

How do you know if your oestrogen levels are high or imbalanced?

According to Mayo Medical Laboratories the following estrone and estradiol levels are considered normal:

For women



Prepubescent female

Undetectable–29 pg/mL

Undetectable–20 pg/ml

Pubescent female

10–200 pg/mL

Undetectable–350 pg/ml

Premenopausal adult female

17–200 pg/mL

15–350 pg/ml

Postmenopausal adult female

7–40 pg/mL

<10 pg/ml

For men



Prepubescent male

Undetectable–16 pg/mL

Undetectable–13 pg/ml

Pubescent male

60 pg/mL

Undetectable–40 pg/ml

Adult male

10–60 pg/mL

10–00 pg/ml

What are endocrine disruptors?

Endocrine disruptors are chemicals that alter the way hormones function. Normally, our endocrine system releases hormones to signal to different tissues what they need to do. When external chemicals enter our bodies, they have the ability to mimic our natural hormones; blocking or binding hormone receptors. This is particularly detrimental to hormone-sensitive organs, like the uterus and the breast, as well the immune and neurological systems, and overall can have a negative impact on human development.

What is oestrogen toxicity and what causes it?

Stress/Poor Sleep

When we are stressed or lacking sleep, our body creates more cortisol. Part of this process involves using up the hormone progesterone, which leaves behind a relative surplus of oestrogen. What’s more, when we don’t sleep enough, our melatonin levels drop, which further exacerbates the problem, since melatonin is a key factor in protecting against oestrogen dominance.


Chemical oestrogens (a type of xenoestrogen) are more present in our environment than ever before and affect both men and women. They can be found in shampoos, conditioners, air fresheners, house cleaners and food (pesticides are another example of xenoestrogens). They disrupt the endocrine system and also mimic the structure of oestrogen.

What are xenoestrogens?

Xenoestrogens are a subcategory of the endocrine disruptor group that have oestrogen-like effects. The body regulates the amount of estrogen needed via intricate biochemical pathways. When xenoestrogens enter the body, they increase the total amount of oestrogen, resulting in a phenomenon called “oestrogen dominance”. Xenoestrogens are not biodegradable, so they are stored in our fat cells. The build up of xenoestrogens has been linked to a variety of chronic conditions, including breast, prostate and testicular cancer, obesity, infertility, endometriosis, early onset puberty, miscarriage and diabetes.

Ways to reduce oestrogen toxicity

  1. Limit your intake of processed foods - BPA (a xenoestrogen) is found in the lining of processed food, which permeates the food stored inside. Always use steel or glass containers, as plastic and styrofoam also release oestrogen-like compounds into food.
  2. Eat more cruciferous vegetables - these contain a powerful antioxidant called Indole 3 Carbinol, which helps to metabolise excess oestrogen. This is found in broccoli, cauliflower and sprouts, amongst other veggies
  3. Ensure you eat organic dairy - that will not have been treated with antibiotics or hormones. Choose grass-fed wherever possible as this will contain higher levels of vitamins and minerals.
  4. Choose organic - for food that is traditionally loaded with pesticides (strawberries, spinach, nectarines, apples, grapes, peaches, cherries, pears, tomatoes, celery, potatoes, sweet bell peppers, hot peppers)
  5. Use flaxseed - in yoghurts, smoothies and salads. These contain phytoestrogens, which have been shown to reduce the risk of breast cancer by helping to block the negative effects of xenoestrogens on your cells.
  6. Eliminate soy products - studies have suggested that soy isoflavones may contribute to breast cancer and also disrupt normal thyroid function.

Ways to reduce xenoestrogens

  • 7+ hours sleep every night
  • Manage stress levels effectively
  • Do regular exercise / stay active day-to-day

Muscle strength & the menopause

Since oestrogen plays a role in preserving healthy bones, you might wonder whether it contributes to muscle strength gains and in growth in response to resistance training. When men experience a drop in testosterone with age, their strength also declines along with it. Is this also true in women? What role does oestrogen play in the loss of muscle strength and size with age?

As you know, both men and women lose muscle size and strength with age, and in women loss of muscle strength accelerates after menopause, corresponding to the time that oestrogen levels drop. Interestingly, women and men have roughly similar muscle strength in the legs when differences in muscle size are taken into account, but this changes after menopause as women lose strength at a faster rate. Since oestrogen is produced by the ovaries, which stop functioning after menopause, it’s easy to see why women are oestrogen-deficient after menopause. However, even post-menopause, most women do produce some oestrogen, since it can be converted from testosterone produced by the adrenal glands.

That’s not the only evidence suggesting that oestrogen plays a role in muscle strength – women who take oestrogen-based hormone replacement therapy do not experience the same degree of strength loss after menopause as women who approach the menopause naturally. Plus, studies in rodents show that mice who have had their ovaries removed have leg muscles that are 10 to 20% weaker than mice who retain their ovaries and thus their ability to produce oestrogen.

Research suggests that oestrogen enhances the ability of muscles to generate force, not by increasing the size of the muscle, but by improving the quality of the muscle tissue. This is possibly due to its effect on the muscle protein myosin. This works in tandem with another protein, called actin, to control muscle contraction.

Does oestrogen enhance muscle recovery?

After strength training, muscles need time to recover. That’s why it is advised to avoid working the same muscle group for at least 48 hours. During the rest and recovery period between workouts, muscles go through a repair process that’s critical for muscle growth. Interestingly, oestrogen seems to reduce the amount of muscle damage that occurs in response to a workout. How might it do this?

According to research, oestrogen acts as an antioxidant, which helps to reduce muscle inflammation. It also helps to stabilise muscle cell membranes. If that’s the case, you might think having more oestrogen would limit muscle growth, since muscle damage is a key stimulus for hypertrophy (muscle-building). However, there’s currently no evidence that oestrogen stimulates or interferes with muscle growth, only that it helps prevent muscle atrophy (muscle breakdown) and preserve muscle strength.

One way it seems to preserve muscle strength and size is by activating satellite cells. These cells are directly involved in strength gains and hypertrophy. In response to the stress of training, satellite cells fuse with muscle cells and donate their own nuclei and contractile proteins to the cells, giving them the ability to contract with greater force. You might also expect this to be a stimulus for muscle growth.

Keeping hormones in balance

There are both natural and medical methods to balance your hormones. The supplement resveratrol has health benefits that may help with balancing oestrogen. Certain foods, such as broccoli and other cruciferous vegetables, may also help to strike a healthy balance. Lifestyle also plays a vital role. Avoiding excessive alcohol consumption is recommended, as this can increase oestrogen production in men. Chemicals in plastics can disrupt proper hormone function, so BPA-free products and avoid microwaving food in plastic containers. Eat organic produce where possible, to lower the number of chemicals and additional hormones in your food. It is best to maintain a healthy weight and body mass ratio, because body fat can contribute to hormonal imbalances.

Oestrogen and weight gain & loss

For women, lower levels of oestrogen can lead to weight gain. This is especially true during the menopause when one form of oestrogen, estradiol, is very low. This hormone plays a key role in regulating metabolism and body weight, so when levels drop, weight gain may become more likely. Lack of oestrogen may also cause the body to use starches and blood sugar less effectively, which would increase the body’s tendency to store fat thus making it harder to lose weight.

Other reasons for low oestrogen levels in women include polycystic ovary syndrome (PCOS, a condition where small cysts are present on the ovaries and imbalances in hormones), lactation, ovary removal, anorexia and vigorous exercise.

Reduced oestrogen may also lower our metabolic rate, the rate at which the body converts energy (food) into working energy or the rate at which the body burns calories. Research is currently looking into whether oestrogen hormone therapy may help to increase a woman’s resting metabolic rate in order to reduce the risk of weight gain during the menopause.


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Published on 25th Feb 19