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PCOS series (part 3) - What are the causes?

In this post I really want to outline the current understanding regarding the causes of polycystic ovarian syndrome (PCOS). Identifying the causes of this condition can ensure you're heading in the right direction when it comes to treating PCOS effectively. I also want to mention that the cause for you might be very different to someone else with the same condition, or there might be several factors contributing to PCOS. This is why I always recommend working with a qualified practitioner (or several) to help identify what's going on for you.

Genetic susceptibility

You may have a genetic susceptibility that increases your chances of having PCOS. There are specific genes that may predispose you to having insulin issues (we'll discuss this more later) or higher testosterone levels. But keep in mind - your environment can influence how these genes are expressed, meaning things like your diet and lifestyle can (in very simplistic terms) turn "on" or "off" certain genes, but you'll still be more susceptible to PCOS than someone who doesn't have those genes.

Blood glucose levels & insulin:

If we are speaking very generally - when weight issues are present, we may see issues with blood glucose and insulin. This is probably the most common driver of PCOS. After a meal, especially one rich in carbohydrates or sugar, our blood glucose levels rise. The pancreas releases insulin in response to the blood glucose rise. Insulin is the key that allows the glucose to leave the bloodstream and enter the cell where the glucose then goes through a series of steps to eventually be used as energy. When this occurs properly, blood glucose fall back down to a normal level. A large majority of women with PCOS have a condition called insulin resistance. In this condition - the pancreas keeps pumping out excess insulin to manage blood glucose levels, but eventually the cells stop responding to insulin, creating insulin "resistance".

Research shows that insulin directly stimulates androgen production in the ovaries as well as increasing LH - the hormone we discussed earlier which impairs ovulation when it is consistently raised. Insulin also reduces something called sex hormone binding globulin (SHBG) - a complex name but essentially a protein that binds to hormones such as androgens - making them inactive in the blood. If we have too little SHBG - the androgens are likely to be more active in the body creating issues such as acne, hair loss and hirsutism. This is the reason why focusing on insulin resistance is so crucial when managing PCOS.

Stress & adrenal dysfunction:

A smaller amount of women with PCOS have elevated adrenal androgens (that is "male hormones" secreted by the adrenal glands - not the ovaries). The primary adrenal androgen we see raised in PCOS is a hormone called DHEAS. This is believed to occur due to an exaggerated stress response, which may be partially due to a genetic predisposition. When DHEAS is elevated in women, we generally see dysregulation of a pathway called the hypothalamic-pituitary adrenal (HPA) axis. Without making this too complex - when we encounter or perceive stress, our brain communicates with our adrenal glands which produce stress hormones to help us "cope" with this stress. Genetics, early life experiences, our lifestyle and the environment may all contributing to a dysregulated HPA axis, contributing to this type of PCOS. People with this type of PCOS may be told they have "lean PCOS" which in my opinion isn't particularly helpful in terms of treatment.


Inflammation is a term thrown around a lot, but this complex process is also a cause of PCOS. Inflammation is a process by which the immune system is stimulated in an attempt to protect and repair in response to infection, damage or toxins (such as those found in cigarettes). In the case of a broken bone or physical trauma, the inflammation is helpful, in chronic conditions however inflammation can get out of hand. Endocrine disrupting chemicals such as BPA have been documented to play a role in the development of PCOS due to inflammatory processes and are a common issue in PCOS patients.

Gut dysfunction:

Following on, inflammation can stem from dysregulated gut function. In particular, more research is showing an association between the gut microbiome (the good and bad bugs in the gut) and PCOS development. PCOS patients have been shown to have lower diversity in the gut microbiome (we want lots of different types of the good guys in the gut), which can impair gut barrier function. Recent studies have shown that higher levels of endotoxins have been found in the blood of those with PCOS. Endotoxins are particles found on the outer parts of harmful bacteria the gut. When they are released from the bacteria, if the gut barrier is disrupted, these particles may enter the bloodstream causing an inflammatory response contributing to inflammatory PCOS.

Post pill:

Finally - PCOS can be triggered in some women after discontinuing use of the oral contraceptive pill. The pill is known to suppress hormone production in order to inhibit ovulation and pregnancy. In doing so, it suppresses androgens. When the pill is stopped, your body tries to re-establish a menstrual cycle and a rebound effect can occur. A surge in androgens after stopping the pill is commonly associated with post pill PCOS. This type of PCOS may be temporary - but working with a qualified practitioner before stopping the pill may help reduce the chances of developing symptoms.


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