Understanding The Connection Between PCOS And Endometriosis: A Gynaecologists Perspective

Recent studies have suggested that a chronic low-grade inflammatory process may be shared in both conditions. They may share inflammatory pathways or the reason for the inflammation. Significant studies in both 2024 and 2025 showed that there may be a genetic link in that certain genes are common to both disorders. 

Polycystic ovary syndrome is primarily a disorder of the part of the brain that controls your menstrual cycle and your hormone production. This can result in a hormone imbalance. The central area of the brain releases a hormone called GnRH, and this release of hormone commences at puberty. However, the release of this hormone occurs in pulses, and the pulses need to be at a set frequency and set strength to achieve a normal menstrual cycle and normal hormone balance. An abnormality of these pulses may result in a disorder of pituitary hormone production, and this in turn may result in a disorder of ovulation, so that you do not produce an egg every month or only some of the months of the year and the amount of oestrogen and testosterone (male hormone that your ovaries release) may vary.  

Because PCOS is a difficult-to-diagnose disorder, we rely on what is called the Rotterdam criteria. This is because it is a very variable disorder that may have different symptoms and signs in different women. The Rotterdam criteria suggest that you need to have two out of  the three following disorders: 

• Signs of excess androgen (male hormone production), such as excess body hair, oily  skin or acne or blood tests indicating raised androgen or male hormone levels  
• Either infrequent or absent ovulation resulting in irregular periods
• Signs of polycystic ovary syndrome involving the ovaries on a pelvic ultrasound – should be performed by a gynaecological ultrasonographer experienced in this field.

Two out of the three of these criteria are required to make the diagnosis of polycystic ovary  syndrome or PCOS which is not always a straightforward diagnosis. 

Endometriosis which has a completely different origin to PCOS is defined by the presence of  disordered glandular tissue, very similar to the glandular tissue that comes away with a period, being located outside of the uterus. Common sites include the ovaries, the pelvic sidewall, the ligaments that hold the uterus in place, especially the uterosacral ligaments at the back of the uterus, the space between the uterus and the bowel and even the bowel surface. The exact cause of endometriosis is unclear. There is a genetic component and there is an inflammatory pathway component, but the initiating event is unclear. As for polycystic ovary syndrome, there are known to be epidemiological and genetic factors.  

Obviously, it is the fact that both of these conditions can share symptoms that raises the possibility of a connection, besides a possible genetic connection. However, there are also some fundamental differences. Endometriosis is primarily an oestrogen-dominant condition where the deposits of endometriosis rely on oestrogen for their activation, and oestrogen is also involved in the inflammatory pathway with this condition. On the other hand, PCOS is largely a male hormone or androgenic disorder resulting in symptoms related quite commonly to excess male hormone.  

However, pelvic pain and reduced fertility are common with both disorders. For this reason, the two conditions may co-exist, a diagnosis may not be clear-cut and appropriate investigations and management are essential.  

So in essence, you may have both conditions and for this reason, specialist management is appropriate where symptoms are significant.

The common symptoms of polycystic ovary syndrome, which as mentioned may be a metabolic disorder or a body chemistry disorder because of the excess male hormone, include: 

• Irregular menstrual cycles or absent periods altogether
• Excess hair growth, especially in areas where hair does not normally grow, such as on  the face and trunk 
• Hair loss due to excess male hormone 
• Acne and oily skin 
• Reduced fertility 
• Metabolic or body chemistry disorders, both due to male hormones and can also include pre-diabetes. 

The common symptoms of endometriosis include: 

• Pelvic pain, which is often chronic 
• Dysmenorrhoea or painful periods, which is also often chronic. 
• Pain during intercourse, which is usually deep pain. 
• Bowel symptoms such as worsening pelvic pain on using your bowels – especially if endometriosis has infiltrated the bowel wall. 
• Reduced fertility  

However, as mentioned above, it is really pelvic pain and reduced fertility that are the common symptoms that co-exist with these two conditions.  

Whenever these symptoms are chronic, debilitating, interfere in any way with your quality of life or are associated with reduced fertility, it is important that you seek an opinion and management.

As mentioned, polycystic ovary syndrome often impacts and interferes with ovulation. This can result in either poor or absent ovulation, making conception difficult or unlikely.  

There are a number of theories as to why endometriosis is associated with infertility. It may involve the inflammatory pathway, or it may involve the production of adhesions and scar tissue. 

tissue between organs. Although the exact mechanism may not be clear, it is known that treatment of endometriosis does significantly improve fertility.

The actual symptoms that a woman is experiencing may suggest polycystic ovary syndrome or endometriosis, or both. In both conditions, further diagnostic procedures may be necessary. With polycystic ovary syndrome, hormone assays, which include measuring male hormone levels, may give us a clue. In both conditions, the use of pelvic ultrasound, especially by an experienced gynaecological ultrasonographer, may be helpful with both conditions. Polycystic ovaries have a definite diagnostic appearance on ultrasound.  Endometriosis, especially if it is what we call deep infiltrative endometriosis, where the lesions are infiltrating into the walls of the bladder or bowel or ligaments supporting surrounding organs, is diagnostic. Superficial endometriosis, which is small deposits on surfaces, may make diagnosis more difficult as they can be difficult to visualise on ultrasound. However, tenderness on certain organs, such as the ovaries and ligaments, on using the vaginal probe and the fact that organs do not slide readily next to one another and appear to be adherent to one another, can be helpful with signs for diagnosis. 

The treatment of polycystic ovary syndrome depends on whether or not you want to conceive and what symptoms are concerning you. If you want to conceive, it may be a matter of using medication to allow you to ovulate. In patients where simple ovulation induction does not seem to help, then IVF and other fertility options may be necessary.  Where your symptoms are primarily related to your excess male hormone and you do not want to conceive, there are a number of drugs or agents that lower your male hormone level or suppress the production of excess male hormone. This often alleviates symptoms.  

Again, the treatment of endometriosis may depend upon the severity of your symptoms and whether or not you want to conceive. There are a number of progesterone-like drugs which  have been shown over a 6-12 month course to both alleviate symptoms and reduce the 

load or amount of endometriosis. Surgical treatment, where areas of endometriosis are lasered or excised, can also be helpful with fertility, but especially for chronic pelvic pain. Which treatment modality best suits your needs to be discussed with your doctor, and your particular symptoms need to be taken into account.  

Women with one or both of these disorders have often had symptoms for some years, and the symptoms may have been or may still be debilitating and stressful. This aspect of chronic gynaecological disorders needs to be addressed. All women need to be given hope that they can be diagnosed and managed appropriately, and both the value of treatment in the short term and long term needs to be considered. There are always ways to improve your quality of life by addressing what symptoms are concerning and need immediate and ongoing support. Diagnostic criteria and the options for treatment are always discussed, and I always put everything we discuss in a written treatment plan so that you can continue to consider your options over the weeks following our consultation.  

It is also important to use evidence-based treatment. There is no point in using a treatment that has not been proven to be successful, and both a scientific approach is necessary but also your general health, wellbeing and concerns need to be addressed. 

Frequently Asked Questions 

Does having polycystic ovary syndrome increase my risk of developing endometriosis? 

Polycystic ovary syndrome, for the large part, has a different aetiology to endometriosis, and although they may co-exist, there is no definite evidence that having polycystic ovary syndrome will increase your risk of having endometriosis. This may change as we learn more about the gene defects associated with both disorders.

What happens if I do not treat my polycystic ovary syndrome or endometriosis?

The only reason for treating these conditions is to improve your quality of life and address symptoms that are of concern. If you are totally free of symptoms and your fertility is not an issue because you either have children or do not want to conceive, then it may be a watch-and-wait scenario that is best. The indication for treatment is to manage symptoms such as pelvic pain or reduced fertility that are of concern and especially if they are interfering with your ability to enjoy life. Chronic symptoms are especially important to manage.

How long does it usually take to get a diagnosis?

Improved ultrasonography and now the use of contrast MRI, and the use of appropriate biochemistry usually mean that a diagnosis can be established over a few weeks. There is always the possibility with endometriosis that a laparoscopy or a surgical diagnostic procedure may be necessary, but again, this is only necessary if symptoms need to be addressed.

With fertility, is IVF my only option?

In polycystic ovary syndrome, usually allowing the woman to ovulate through medication will significantly improve your chances of conceiving.  

Again, with endometriosis, the treatment of the underlying condition has been shown to improve your chances of conceiving. However, with both conditions, IVF may be necessary if, despite addressing the underlying disorder, pregnancy does not occur, and this can be for unknown reasons.