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What Causes PCOS

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The most important thing to do when diagnosed with PCOS is learn. 

The troublesome thing about PCOS is that it can be caused by many different things, and usually by more than one at a time. It can be overwhelming. But really it isn’t – don’t panic! If you start from the beginning, (and read posts like this one!) hacking PCOS is a breeze.

Step 1 for overcoming PCOS is to learn about the possibilities for what causes PCOS. Step 2 is to learn about your own body. Then you can combine what you know about PCOS and your body, and you can start experimenting with the right diet and lifestyle strategies for you.

My personal contribution to the world’s understanding of PCOS is this precise specialty. Most researchers, doctors, medical professionals, and bloggers focus on only one or two of the potential causes of PCOS. It was very rare, before I started blogging, for bloggers to address or even to know about the many various, complex causes of PCOS. But because I personally didn’t fit the typical PCOS mold, I set out to unearth the underlying complexities of the condition.

I did after several years unearth them, and I overcame my own PCOS with what I learned. Then I wrote an info-packed manual on how to do precisely what I did, and I wrote blog posts like this one. This post is a brief overview of many of the causes of PCOS, designed to help you get started thinking about your own case and what you can do about it.

Skewed opinions on what causes PCOS

I mentioned that the vast majority of doctors, medical professionals and bloggers don’t fully understand PCOS. This is because the majority of women who have poly cystic ovaries — about 65% — suffer from similar underlying health issues. The remaining 35%, however, are much different. And still yet everyone who has PCOS can suffer from multiple causes of PCOS, regardless of whether they are more like the 65% or more like the 35.

Most women who suffer from PCOS are overweight and/or insulin resistant. The cure for them is apparently simple – lose weight and sharpen insulin sensitivity. Yet hypothyroidism, stress, nutrient deficiencies, gene mutations, and birth control pill use are other common influences on the PCOS of these women. This is a problem, because their PCOS is not properly treated.

Other women who are not overweight or insulin resistant almost always completely fall through the cracks at doctor’s offices. They are told to lose weight, but that doesn’t help them. In fact, it makes their type of PCOS worse. They can also suffer from many various causes of PCOS – but these are hardly addressed by medical practitioners at all.

Most people focus on the overweight and insulin resistant aspects of PCOS. But this does an incredible disservice to the many millions of women who suffer from PCOS – because even while that’s a big part of it, that’s not the whole story. I became a part of this world because I wanted to tell the whole story.

What is PCOS?

PCOS stands for ‘poly cystic ovarian syndrome.’ It is the condition of having multiple small cysts on the ovaries. It is normally diagnosed when a woman stops menstruating, or when she tries to conceive a baby but fails. PCOS causes infertility and irregular or missed menstrual cycles. Other common symptoms are acne, hirsutism (facial hair growth), balding, low sex drive, weight gain or difficulty with weight loss, and mental health disturbances.

PCOS is often simply (and erroneously) attributed to one of its most popular causes: insulin resistance.This is wrong because PCOS is not a problem solely of insulin resistance, but is instead a problem of hormone imbalance.  Insulin resistance causes hormone imbalance, but so do many, many other things.

Somewhere around 15% of women in the Western world have PCOS – and this number is increasing.

What Causes PCOS and Why

What Causes PCOS: Insulin Resistance 

Insulin resistance is the state in the body that directly precedes diabetes. In diabetes, the body has been so flooded by blood sugar and insulin that the pancreas shuts down, and it needs insulin injections in order to keep the amount of sugar in the blood from becoming toxic.

Sugar is necessary to have in the bloodstream, but too much is incredibly problematic. Therefore the body has to keep a tight leash on sugar levels. To do so, it uses insulin. The pancreas produces insulin, and the insulin then transports the sugar in the blood to fat cells in order to be stored as energy. When the body is insulin resistant, the fat cells can no longer “hear” this signal, so the body keeps creating more and more insulin in an effort to get the signal “heard.”

Insulin stimulates testosterone production, which will cause hormone imbalance when created in excess. This is the most common cause of PCOS in the world – though it is by no means the only one.

What Causes PCOS: Being Overweight

Being overweight is another common trait of women who have PCOS. It affects about 60% of women who have PCOS.

The relationship between being overweight and PCOS is not 100% clear. Many very smart people believe that insulin resistance is caused by being overweight, so it’s possible that being overweight is the primary problem for a lot of women with PCOS.

Yet others believe that insulin resistance causes people to become overweight, which reverses the causality. I personally think it’s more complicated than both of these cases, and that insulin resistance and being overweight often occur together, though not always.

Being overweight also causes inflammation, which can cause testosterone levels to rise and nutrient deficiencies to become more problematic, as well as thyroid hormone levels to fall. There are many ways that being overweight can cause PCOS. The takeaway point here is that even while we cannot pinpoint why exactly for everyone with PCOS (and it probably varies), being overweight is a part of the PCOS problem for many women.

What Causes PCOS: Dramatic weight loss

PCOS is all about hormone balance. Specifically, it involves elevating male sex hormones like testosterone over female sex hormones like estrogen and progesterone.

Weight loss can trigger this kind of hormone imbalance if the body perceives the weight loss as a significant deprivation of energy from the body. There is a specific command center of the brain called the hypothalamus, and the hypothalamus receives signals from metabolic hormones and fat cells that tell it how well fed you are.

It is important for a woman’s body to always feel fed. When it does not feel fed, it shuts down reproduction. This makes evolutionary sense. Back in the days when humans roamed the savannah, it was a very bad idea to become pregnant during a time of famine. To prevent against that sort of thing, the female body developed a very sensitive hormone system.

This hormone system shuts down when it thinks it is being starved.

Dramatic weight loss is one of the ways in which it may feel starved. This is of course not the case for everybody who loses weight, but it does happen to some women.

What Causes PCOS: Low body fat 

Much like dramatic weight loss, having a very low body fat percentage is another signal to the body that it is being starved. Often for women with PCOS it is hard to tell if it is the rapidity of the weight loss that caused PCOS, or if it was the amount of weight loss that caused PCOS.

In my practice, I find that it is the amount of weight loss that causes PCOS more often, but both do definitely happen.

When body fat percentage is too low, pituitary hormone production shuts down, and often PCOS results.

What Causes PCOS: Overexercising

Overexercising is yet another way to signal to the female body that it is being starved.

You may not feel like you ‘starve’ yourself per se. But exercise requires a lot of calories. If you burn more calories than you eat on a regular basis and do not have ample fat stores to burn, then your body may interpret this as ‘starving.’

What qualifies as overexercising varies from woman to woman. It’s detrimental effects also build up over time. The longer the female body is in a caloric deficit, the more hormone balance suffers.

What Causes PCOS: Stress

Hormone production occurs via something called a ‘cascade.’ The body starts producing hormones with one substrate, and then produces more and more hormones in a series that branches out and multiplies. What happens at the beginning of the cascade is therefore crucial for the later outcomes.

One of the very first ‘decisions’ the body has to make when it produces hormones via this cascade is whether it wants to make stress hormones or sex hormones. It cannot make high amounts of both for any extended period of time – it simply cannot.

If under any sort of emotional or cognitive stress (physical stressors like overexercising, inflammation, or bingeing or restrictive eating count, too), the body interprets this as a need for stress rather than sex hormones. As a result, estrogen and progesterone levels fall. LH and FSH will most likely fall. Sometimes testosterone will, too. Cortisol, the main stress hormone, and DHEA-S, another important if less well-known stress hormone, increase. This is problematic especially for PCOS because DHEA-S is an androgen – a male sex hormone.

PCOS occurs when male sex hormones are elevated over female sex hormones.

What Causes PCOS: Hypothyroidism

Healthy thyroid function is crucial for healthy reproductive function. The thyroid system is responsible for delivering energy to cells. If reproductive cells don’t get the amount of energy they need, they lose their ability to function properly. There is a very clear and strong link between hypothyroidism and PCOS.

There are many different ways that the thyroid gland can malfunction. The two primary ways are 1) via the autoimmune conditions Hashimoto’s Thyroiditis (see a great book on Hashimoto’s here), or 2) via the negative effects of stress on the liver’s ability to make the most important of the thyroid hormones, T3. A low carbohydrate diet can negatively impact T3, too.

PCOS patients who present with subclinical levels of thyroid hormone often begin ovulating once regular thyroid functioning is achieved.  One of my favorite articles reports that thyroid hormone replacement therapy achieves a “significant reduction in total as well as free testosterone,” and also states that “ovarian volumes of patients with hypothyroidism were significantly great compared with controls, and their magnitudes diminished significantly during thyroid hormone replacement therapy.”

What Causes PCOS: Environmental toxins

Almost all non-organic fruits and vegetables are covered in chemicals that act as phytoestrogens in the body. Over time, specifically when young, these can have a major impact on reproductive physiology.  Some foods are worse than others. The way to mitigate this is to eat organic, to peel vegetables, or to wash them with organic soap.  A great way to wash vegetables is to soak them in vinegar for several minutes.  Vinegar binds with some of these toxins and will help chelate them off of the skin of the vegetables.

A second endocrine disruptor, perhaps the most prevalent one in American lives today, is BPA. BPA is a polymer leached from plastics (though it is not the only one – thus why I recommend using glass tupperware) that disrupts endocrine function in a way not entirely yet understood, but appears to have negative effects on hormone balance.

When rats are exposed to BPA, their male offspring have decreased fertility, and only after exposure to small doses.  Of the male rats, one study concludes:

“The BPA exposed males had a suite of reproductive deficiencies that collectively created subfertility in the rats. Some of these included lower sperm counts, poor sperm motility and cellular defects within the testes. Circulating levels of testosterone, estrogen and other reproductive hormones were also significantly lower.

The BPA exposed males were also significantly heavier than unexposed controls.

Female rats are affected just as strongly, if not worse.  THEY GET PCOS. They has cystic ovaries, increased estrogen and testosterone levels, and decreased progesterone. Progesterone is absolutely crucial for a healthy menstrual cycle.

Similar resuts have been reported in human females.  Women with PCOS, both lean and overweight women, have 40 percent higher levels of BPA in their blood than those without.  Notably, the levels are even more markedly increased in thin women with PCOS.  In thin women, PCOS patients had 1.6 times ordinary BPA levels, and in overweight women the ratio was just 1.3.  Some researchers speculate that this is because BPA is being stored in fat cells, while other posit that BPA causes brain-related hormone signaling dysfunction, which could explain why so many people end up having PCOS at all.

Hard plastics, the polycarbonate plastics such as #7, are worse than soft plastics.  Plastics 1, 2, and 4 seem to be BPA free. Heated plastics leach at much higher rates than cold ones. Research has shown that BPA gets into bodies in even higher doses from eating out of aluminum cans than out of plastic.  Cans are lined with BPA on the inside, so virtually everything eaten out of a can is swimming in BPA.   Here’s a  list of consumer tips.

Another source of environmental estrogens is body applications.  Parabens are phytoestrogens and are one of the most common elements in lotions and soaps. Receipts, oddly, are also very high in BPA and estrogenic supplements. Many cashiers wear gloves for this reason.

What Causes PCOS: Birth Control Pill Use

The birth control pill has a varied and complex effect on women’s reproductive health. Some women deal with it just fine. Others, not quite so much. Usually the problem happens when a woman stops taking BCPs: while on the BCP, women’s bodies often adjust to the exogenous hormone input. When coming off of BCP, the liver, hypothalamus, and pituitary gland all need to readjust to natural hormone production. This process can take a long time and will very often cause the symptoms of PCOS.

For more on birth control and how to manage it’s physical effects, you can check out my small book on the topic, Birth Control Unlocked.


What Causes PCOS: Pituitary or hippocampal tumors

If LH, FSH, TSH, or Gonadotropin Releasing Hormone levels are significantly impaired, and if all other causes have been ruled, this is an indicator that an MRI should be performed.

Diet and PCOS

It almost goes without saying that diet plays a critical role in PCOS – perhaps the most critical of all. I have in fact written a 140 page-long book on the topic.

There are many foods to put on a watch list, depending on what the underlying issue is for you. For example, if Hashimoto’s thyroiditis is your primary problem, the autoimmune-problematic foods such as grains should be avoided at all costs. I do not list these foods here – their roles are instead wrapped up with all of the causes of PCOS listed above.

There are a handful of foods that may have a direct effect on hormone balance all on their own. They are:

-Soy, flax and other phytoestrogens.  Phytoestrogens resemble– but are not chemically the same as–estrogen in the body. This leads to confusion in the endocrine system (and, significantly, breast cancer.) Remarkably, soy may play a greater role in endocrine disruption than BPA.

-Dairy. Pregnant cows produce a protein that inhibits testosterone binding mechanisms, such that dairy is the most androgenic category of foods. This spans butter, milk, yogurt, cream, and any product from a pregnant cow.  Moreover, dairy also has a significant insulin response, which can irritate acne and PCOS.

– Factory farmed meat. Conventional meat is injected with Bovine Growth Hormone, which can increase insulin-like growth factor 1 in humans.  Perhaps worse, other hormones such as estrogen and testosterone are approved by the FDA for injection into the animals via an earpiece each animal is implanted with at birth. The FDA claims that even with supplementation the animal’s hormonal profile falls within normal ranges, but I remain skeptical.

– Cruciferous vegetables.  The vast majority of the time greens are incredibly healthy. Nevertheless there is a limit to all things. Leafy greens can act as goitrogens and can decrease thyroid functioning when eaten raw and/or in very high doses.

For more information…

Here in this post, I summarize the most common ways in which women develop PCOS. This information was put together after years of research and theorizing – it’s not common to pay so much attention to the various causes of PCOS. Nevertheless I have found it to be incredibly successful in helping women manage and overcome PCOS. Each woman’s PCOS is unique, and we all need to find our root causes in order to heal.

If you’d like to learn how did it, learn more about what causes PCOS and what may be causing your PCOS, and how I’d recommend managing it, you may want to check out PCOS Unlocked: The Manual, the multi-media resource I created to help you with your PCOS.



So what do you think?  What causes PCOS? What is the cause of your  PCOS?  What did you  do to overcome it?!


So, just as a heads up - some links above may be my affiliate links, which means I get a small commission if you click on it and make a purchase. Doing so is no additional cost to you, but helps me tremendously. Your support is SO greatly appreciated, so thank you in advance if you choose to do so. Check out my entire disclosure to know exactly how things work.

Managing director of Paleo for Women and author of Sexy by Nature.


  1. Pingback: Paleo and PCOS | Paleo For Women

  2. Wow, this website is good. I know it’s only a matter of time before people start trickling over here. Very informative, technical, and research based. I’ve done a lot of research myself about the issues on this website due to my own health struggles to regulate my endocrine system/hormones and find this information to be right on with cutting edge about HPA axis imbalance. Kudos.

  3. Have you read “Why Do I Still Have Thyroid Problems When My Test Results are Normal?” It explains why supplementing with iodine is one of the worst things you can do for hypothyroidism.

  4. Thanks for the great articles on PCOS and Paleo. I was recently diagnosed with PCOS and am in the processing of reading up on it. One thing I would like to point out about this post is regarding #5 Factory Farmed Meat is not completely accurate. All chicken produced in the USA is hormone free regardless of what the package says (or does not say). Per FDA regulations the use of hormones is prohibited in chickens and has been since the 1960s or 1970s. “Hormone Free” on a package of chicken is nothing more than a marketing ploy to get you to spend more money on that package of chicken versus your other cheaper options. This was a ploy started by Perdue Chicken in the 1990s and was actually challenged in the court system. The courts ruled that this was not false advertising since all chicken is indeed “Hormone Free.” However, the real application of this marketing has given the general public the perception that if some chicken is advertised as “Hormone Free” then the others must have hormones in it. The only hormones found in chicken are the ones naturally made by the chicken which you cannot avoid. My husband has a PhD in animal nutrition and works as a Poultry Nutritionist. Consequently, in addition to the regulations I also have firsthand knowledge of what goes into a chicken ration an it does not include hormones.

    • Hm, thank you, Rachel. I have thought about this often, and read many conflicting stories. Glad to have an unbiased source (of a sort :) ) weigh in. I also feel quite strongly that the bigger problem for animals is what they themselves eat. I find that pasture raised eggs do not give me problems, but that those fed “vegetarian soy diets” do give me acne. At least that was my experience several months ago when I was experimenting with that sort of thing.

      • Take out any ethical/moral/legal issue of feeding hormones to chickens and just think about the financial implications. In a GOOD year a poultry producer can hope to make 1.50 per lb of white meat. Most recently I think the average rate is closer to 0.90 lb right now. There is no way the producers can cover the cost of injecting steroids (aka hormones) into chickens and hope to recoup their cost much less make a profit doing so. If you ever have any questions about the diet composition of poultry or swine then let me know. My husband works with both on a regular basis. Were your pastured eggs from a local small farmer or just ones you could buy in the store? If they were ones in the store I would imagine those chickens were fed some kind of diet in addition to what they were able to find while outside. The problem with all veg diets for chickens is that they have to have some type of fat source in the feed. If they are eating all veg diets then it has to come from soy beans. Non veg chicken rations do not usually have as much soy in them. A standard chicken ration usually includes corn, soy, sometimes wheat and other grains (depending on the time of year), fat source, amino acids (proteins, needed because the typical corn soy diet is deficient in some essential amino acids needed for the bird to grow), vitamins, minerals, and usually a few enzymes. Extensive research has been done on the nutritional needs of a bird in order to make it grow as efficiently and cheaply as possible in a short amount of time (usually 42-60days).

      • That happens to me also with those eggs. I thought it might have something to do with the Omega 3 supplementation which usually goes along with these vegetarian and soy diets for chickens.

  5. Pingback: Inspired Fit Strong – PCOS: What is The Root Cause of It and What Could be The Treatment?

  6. Pingback: Inspired Fit Strong – СПКЯ: Каква е причината за Синдрома на поликистозните яйчници и как да се справите с него

  7. Awesome blog you have here but I was wondering if you knew of any
    message boards that cover the same topics talked about in this article?
    I’d really love to be a part of online community where I can get
    advice from other experienced individuals that share the same interest.

    If you have any recommendations, please let me know.

  8. I want a reveiw or research paper about polycystic ovaries due to broiler chicken if you have then plz sebd me I’ll very thankfull to u. Your effort is great and your work is very interesting:-) keep it up

  9. Pingback: Paleo and Women – Belly Fat, Infertility, Menopause | Teresa Wymore

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