PCOS and insulin resistance: what connects them?

PCOS and insulin resistance are often mentioned together. This can give the impression that they are two names for the same problem, or that everyone with PCOS must have an abnormal insulin result. In reality, these are two distinct phenomena that frequently overlap and can reinforce each other.

PCOS is a complex hormonal and metabolic disorder. Insulin resistance, on the other hand, means a reduced response of tissues to the action of insulin. It can occur in people with PCOS, but it is not required to make that diagnosis. Conversely, insulin resistance alone does not mean that a person has PCOS.

Understanding this difference is important, because it makes it possible to choose the right tests and treatment. Not everyone needs an "insulin curve", metformin, weight loss, or a very restrictive diet.

What is PCOS?

PCOS is a set of symptoms resulting from disturbances in the hormonal and reproductive systems. It can also affect metabolism, diabetes risk, lipid balance, sleep, and mental well-being.

In adults, the diagnosis is based on the presence of at least two of three features:

1. ovulation disorders, which may present as irregular or infrequent periods,
2. clinical or laboratory hyperandrogenism, meaning excessive action of androgens,
3. characteristic ovarian morphology on ultrasound or, in appropriately selected adult cases, an AMH result.

Before making the diagnosis, other possible causes of the symptoms must be excluded, including thyroid disorders, hyperprolactinemia, non-classic adrenal hyperplasia and, depending on the clinical picture, other hormonal conditions.

If an adult has both irregular cycles and hyperandrogenism at the same time, ovarian ultrasound is not always necessary. AMH, however, should not serve as a single test decisive for a PCOS diagnosis.

The most common symptoms of PCOS

The presentation of PCOS can differ between patients. Possible symptoms include:

• irregular periods,
• long cycles or absence of menstruation,
• problems with ovulation and fertility,
• excessive facial or body hair,
• acne,
• oily skin,
• thinning of scalp hair,
• easier weight gain,
• difficulty losing weight,
• glucose disturbances,
• low mood, anxiety, or dissatisfaction with one's own body image.

Not everyone has all the symptoms. PCOS can occur both in women with higher body weight and in lean women.

What is insulin resistance?

Insulin is a hormone produced by the pancreas. It facilitates the transport of glucose from the blood into cells, where it can be used as a source of energy or stored.

In insulin resistance, tissues respond more weakly to the action of insulin. The pancreas may then increase its secretion in order to maintain a normal glucose level. For some time, fasting glucose can remain normal, even though the body needs increasingly more insulin.

Over time, the compensatory mechanism may cease to be enough. This can lead to:

• abnormal fasting glucose,
• impaired glucose tolerance,
• prediabetes,
• type 2 diabetes.

Insulin resistance is not, however, diagnosed on the basis of a single universal insulin threshold. Available insulin assays are not sufficiently standardised, and values depend, among other things, on the laboratory method used. You can read more about interpreting these results in the article on insulin, glucose, HOMA-IR and HbA1c.

PCOS versus insulin resistance: the key differences

How can insulin resistance worsen PCOS symptoms?

The relationship between PCOS and insulin is multidirectional. Insulin resistance can affect not only glucose levels but also androgen production and ovarian function.

1. The pancreas produces more insulin

When tissues respond more weakly to insulin, the body tries to compensate by increasing its secretion. Hyperinsulinemia appears, meaning an elevated concentration of insulin in the blood.

Glucose may still fall within the reference range at this time. For this reason, a normal fasting glucose result does not always show the full picture of carbohydrate metabolism.

2. Insulin can increase androgen production

A high concentration of insulin can stimulate the theca cells of the ovary to produce androgens. At the same time, it can enhance the action of luteinizing hormone, which also participates in regulating hormone production by the ovaries.

As a result, symptoms such as the following may intensify:

• excessive hair growth,
• acne,
• thinning hair,
• ovulation disorders,
• irregular periods.

3. Insulin can lower SHBG levels

SHBG is a protein produced mainly in the liver. It binds part of the sex hormones, including testosterone.

Hyperinsulinemia can reduce SHBG production. In that case, a larger portion of testosterone remains in the free, biologically active form. This means that symptoms of hyperandrogenism can worsen even when total testosterone is not very high.

4. Androgens can worsen insulin sensitivity

The relationship can also work the other way around. Excessive action of androgens can affect the distribution of adipose tissue, the functioning of muscles, adipose tissue and the liver, and can intensify disturbances in insulin signalling.

A vicious circle mechanism arises:

insulin resistance → greater insulin secretion → greater androgen activity → further worsening of metabolism.

Contemporary research also points to the importance of disturbances in insulin signalling pathways, chronic inflammation, mitochondrial function, GLUT4 expression, circadian rhythm, and genetic and epigenetic factors. A large part of the detailed mechanisms, however, still requires confirmation in high-quality studies involving humans.

How does this look in practice?

Does everyone with PCOS have insulin resistance?

No.

Insulin resistance is an important element of the PCOS mechanism, but it does not occur to the same degree in everyone. Its frequency depends, among other things, on:

• the PCOS phenotype,
• age,
• ethnic background,
• the amount of visceral adipose tissue,
• physical activity,
• genetic predispositions,
• the method used to assess insulin resistance.

PCOS can occur in a person who is lean, active, and has normal glucose. Such a person may still require an assessment of metabolic risk, because the increased risk of impaired glucose tolerance in PCOS occurs independently of BMI.

This does not mean, however, that every lean person with PCOS has "hidden insulin resistance" that must necessarily be found using an extensive insulin curve.

Does everyone with insulin resistance have PCOS?

No.

Insulin resistance can occur in connection with, among other things:

• genetic predispositions,
• a higher amount of visceral adipose tissue,
• low physical activity,
• lack of sleep,
• obstructive sleep apnoea,
• the use of certain medications,
• puberty,
• pregnancy,
• menopause,
• liver diseases,
• Cushing's syndrome,
• other hormonal disorders.

Elevated insulin alone therefore does not confirm PCOS. The diagnosis requires an assessment of the cycle, symptoms of hyperandrogenism, hormone results, and possibly ovarian morphology. If you are looking for a starting point, see how to recognise insulin resistance and what to do without medication.

Is insulin resistance a diagnostic criterion for PCOS?

No. Insulin resistance is not among the three basic diagnostic criteria for PCOS.

To make the diagnosis, none of the following is required:

• an elevated fasting insulin result,
• an abnormal HOMA-IR,
• a characteristic insulin curve,
• overweight or obesity,
• an abnormal glucose result.

You can therefore have PCOS with normal insulin and glucose results. You can also have a high insulin concentration without PCOS.

Is it worth testing fasting insulin and HOMA-IR?

This is one of the most common questions that come up with PCOS.

International guidelines indicate that insulin resistance plays an important role in the PCOS mechanism, but clinically available insulin assays have limited usefulness. They are not recommended as a routine diagnostic tool or as a basis for diagnosing PCOS.

Why can a single insulin result be difficult to interpret?

The result is influenced by, among other things:

• the method used by the laboratory,
• the time since the last meal,
• sleep,
• stress,
• activity from the previous day,
• infection,
• medications taken,
• the phase of the cycle,
• the way the sample was prepared for.

No single, universally binding HOMA-IR threshold has been established for all age groups and populations. The result should therefore not be interpreted in isolation from the other tests and the clinical picture.

An insulin measurement can be used in scientific research or in selected clinical situations. It should not, however, serve for the automatic diagnosis of PCOS or for assessing treatment effectiveness on the basis of a single value.

Which test best assesses carbohydrate metabolism in PCOS?

According to international guidelines, the most accurate test assessing glycaemia in people with PCOS is the oral 75 g glucose tolerance test, or OGTT.

The test makes it possible to assess fasting glucose as well as its concentration after drinking a glucose solution. It can detect impaired glucose tolerance that is not visible in the fasting result.

If the OGTT cannot be performed, fasting glucose or HbA1c can be considered. It must be remembered, however, that in PCOS they have lower sensitivity than the glucose tolerance test.

It is important to distinguish two issues:

• the OGTT assesses the way the body deals with glucose,
• it is not a direct and universal test confirming insulin resistance.

Which tests are worth considering in PCOS?

The scope should be determined individually. Not everyone needs all the measurements at once.

In everyone with diagnosed PCOS, glycaemia should be assessed regardless of age and BMI. A lipid panel is recommended at diagnosis, while blood pressure should be measured at least once a year.

How often should glycaemia be monitored?

After a normal result, carbohydrate metabolism should be reassessed after about one to three years. The exact timing depends on individual risk.

More frequent monitoring may be needed with:

• prediabetes,
• a history of gestational diabetes,
• higher body weight,
• an increasing waist circumference,
• low physical activity,
• type 2 diabetes in the family,
• taking medications that affect glycaemia,
• earlier results close to borderline values.

Large population studies confirm that women with PCOS have an increased risk of developing type 2 diabetes. The risk increases further with higher BMI, but is not limited only to people with obesity.

PCOS, insulin resistance, and body weight

A higher amount of visceral adipose tissue can worsen insulin sensitivity, increase inflammation, and intensify androgen production. This does not mean, however, that body weight is the sole cause of PCOS.

PCOS also occurs in lean people. On the other hand, not everyone who is overweight or obese has PCOS.

A conversation about treatment should not be limited to the instruction "please lose weight". What also matters is:

• the quality and regularity of meals,
• physical activity,
• sleep,
• stress levels,
• mental health,
• hormonal symptoms,
• plans regarding pregnancy,
• medications taken,
• individual possibilities and barriers.

Current guidelines emphasise that a healthy lifestyle can bring metabolic and health benefits even without weight loss.

Is a special diet necessary in PCOS?

There is no single diet that would be best for everyone with PCOS.

Research does not confirm that one specific distribution of protein, fat, and carbohydrates is clearly better than the others in terms of body weight, hormones, metabolism, fertility, or well-being.

The way of eating should be:

• sustainable,
• nutritionally complete,
• adapted to preferences,
• adjusted to test results,
• appropriate to the level of activity,
• free of unnecessary eliminations.

Guidelines advise against overly restrictive and unbalanced diets.

What can help in practice?

Depending on needs, it is worth paying attention to:

• a protein source in main meals,
• vegetables, fruit, whole grains, and other sources of fibre,
• legume seeds, if they are well tolerated,
• unsaturated fats,
• limiting frequent consumption of sweetened drinks,
• reducing the share of highly processed snacks,
• adjusting portion sizes to needs,
• regularity matching the individual's daily routine.

Not everyone with PCOS has to eat five meals. Nor does everyone have to eliminate gluten, dairy, fruit, carbohydrates, or products with a higher glycaemic index.

What matters most is the whole way of eating, not a single product.

Is a ketogenic or very low-carbohydrate diet necessary?

No.

Reducing the amount of highly processed carbohydrates and sweetened products can improve the quality of the diet, but this does not mean it is necessary to eliminate all sources of carbohydrates.

A diet very low in carbohydrates can be difficult to maintain, increase the risk of deficiencies, and intensify a restrictive approach to eating. If it is being considered, it should be adapted to the state of health, preferences, and possibilities of the patient.

In PCOS, no superiority of one dietary composition over the others has been demonstrated.

What role does physical activity play?

Physical activity can improve insulin sensitivity, the lipid profile, fitness, body composition, and well-being.

There is no single type of training that would be best for everyone with PCOS. Benefits can come from:

• strength training,
• brisk walking,
• cycling,
• swimming,
• running,
• interval training,
• dancing,
• daily activity of lower intensity.

Adults should ultimately aim for 150–300 minutes of moderate-intensity aerobic activity per week or 75–150 minutes of vigorous activity. It is also worth including muscle-strengthening exercises. There is no need, however, to start at the full recommended level. Any reduction in time spent sitting can be beneficial.

Metformin in PCOS

Metformin increases tissue sensitivity to insulin and reduces glucose production in the liver. It can be used in PCOS mainly to improve metabolic parameters.

Current guidelines indicate that metformin should be considered in adults with PCOS and a BMI of at least 25 kg/m², particularly in the context of glycaemia, insulin resistance, lipids, and anthropometric parameters.

In people with a BMI below 25 kg/m² it can also be considered, but the quality of available evidence is more limited.

The decision should take into account:

• test results,
• diabetes risk,
• tolerance of the medication,
• reproductive plans,
• other treatment being used,
• the patient's preferences.

Metformin is not a medication that "removes PCOS". Not everyone with PCOS needs it simply because they have irregular periods or a single high insulin result.

The most common side effects concern the gastrointestinal tract. Gradual dose increases and extended-release formulations can improve tolerance. With long-term use, particularly in people with deficiency risk factors, it is worth considering monitoring of vitamin B12.

Hormonal contraception and insulin resistance

Combined hormonal contraception can be used in the treatment of irregular periods, acne, and hirsutism. Its main goal, however, is not the treatment of insulin resistance.

The choice of preparation should take into account:

• thromboembolic risk,
• blood pressure,
• smoking,
• migraines,
• body weight,
• the lipid profile,
• individual contraindications.

Guidelines indicate that hormonal contraception may be preferred for irregular periods and hyperandrogenism, while metformin more often serves to achieve metabolic goals.

Does inositol help?

Inositol is often marketed as a natural alternative to metformin. Available studies suggest the possibility of some improvement in selected metabolic parameters, but the clinical benefits remain limited and uncertain.

At present, it is not possible to indicate a single best:

• type of inositol,
• ratio of myo-inositol to D-chiro-inositol,
• dosage,
• duration of supplementation.

Guidelines indicate that metformin has better-documented action in terms of central adiposopathy and hirsutism, although it more often causes gastrointestinal complaints. In the treatment of infertility, inositol is still treated as an experimental therapy.

Will treating insulin resistance restore regular periods?

It may help, but it does not guarantee it.

Improving insulin sensitivity and reducing hyperinsulinemia can limit excessive androgen production and support ovulation. The effect, however, depends on the PCOS phenotype, the degree of hormonal disturbances, body weight, age, and other health problems.

Absence of menstruation may require additional treatment to protect the endometrium, even if metabolic measures are being pursued at the same time.

If the main goal is pregnancy, treatment should be adapted to fertility. Current guidelines indicate letrozole as the first-line treatment for ovulation induction in women with PCOS who do not ovulate and have no other diagnosed causes of infertility.

The most common misconceptions

Summary

PCOS and insulin resistance are strongly connected, but they are not the same thing.

Insulin resistance can lead to increased insulin secretion, intensify androgen production, lower SHBG, and disturb ovulation. Excessive action of androgens can at the same time worsen metabolism, creating a mechanism of mutual reinforcement.

Not everyone with PCOS, however, has confirmed insulin resistance, and insulin resistance alone does not mean PCOS. Nor is it one of the diagnostic criteria for this syndrome.

In metabolic assessment, a properly chosen evaluation of glycaemia is more important than a random insulin result, particularly the OGTT, a lipid panel, blood pressure, and analysis of the whole clinical picture.

Treatment should respond to the patient's real needs. It may include the way of eating, activity, improving sleep, metformin, hormonal treatment, fertility support, or pharmacological treatment of excess body weight. There is no single scheme appropriate for everyone.

This material is educational in nature and does not replace an individual medical consultation. A diagnosis of PCOS or insulin resistance should not be made on the basis of a single laboratory result.

Frequently asked questions

Can you have PCOS with normal fasting insulin?

Yes. Insulin resistance is not a required criterion for diagnosing PCOS. Moreover, a single insulin result does not fully show tissue sensitivity to its action. PCOS can be diagnosed on the basis of ovulation disorders, hyperandrogenism, and characteristic ovarian morphology, after other causes have been excluded.

Can you have PCOS and a normal body weight?

Yes. PCOS also occurs in lean women. A normal BMI does not rule out ovulation disorders, hyperandrogenism, or an increased risk of impaired glucose tolerance. That is why an assessment of glycaemia is recommended regardless of body weight.

Does a HOMA-IR result confirm insulin resistance?

HOMA-IR can be a useful indicator in scientific research and selected clinical situations, but there is no single threshold binding for everyone. The result depends on the insulin assay, the method used, age, and the population studied. It should not decide on the diagnosis or treatment on its own.

Do you need an insulin curve in PCOS?

It is not routinely recommended by international guidelines. In assessing carbohydrate metabolism, the OGTT with glucose measurement is recommended above all. Insulin assays have limited standardisation and should not be automatically performed in everyone with PCOS.

Does normal fasting glucose mean everything is fine?

Not always. Fasting glucose can be normal, while abnormalities appear only after drinking a glucose solution. That is why the OGTT is considered a more accurate test for assessing glycaemia in PCOS.

Does PCOS lead to diabetes?

PCOS increases the risk of prediabetes and type 2 diabetes, but it does not mean the disease will definitely develop. Genetics, body weight, activity, sleep, diet, medications, and diabetes in the family also matter. Regular monitoring of glycaemia allows early detection of changes.

Do you have to give up fruit with PCOS?

No. Fruit can be part of a nutritionally complete way of eating. It provides fibre, vitamins, minerals, and bioactive compounds. What matters most is the overall diet, the amount of energy consumed, and the frequency of consuming sweetened drinks and highly processed products.

Do you have to eat meals every three hours?

There is no single meal frequency appropriate for everyone with PCOS. For one person, three larger meals will work well; for another, four smaller ones. The plan should take into account hunger, satiety, activity, working hours, medications taken, and the ability to maintain regularity.

Does metformin help with weight loss?

Metformin is not a typical weight-loss medication. In some people it can support a slight reduction in body weight or limit its gain, especially when metabolic disorders coexist. Its primary role in PCOS is to improve selected metabolic parameters. The response to treatment is individual.

Is metformin needed with normal glucose?

Not always. The decision should not result solely from fasting glucose. The doctor takes into account, among other things, the OGTT result, BMI, diabetes risk, the lipid profile, a history of gestational diabetes, previous treatment, and the patient's goals.

Can inositol replace metformin?

It should not be treated as an equivalent substitute. Inositol can be considered after discussing the limitations of available evidence. No single best preparation or dosage has been established, and metformin has better-documented metabolic action in PCOS.

Is weight loss always necessary?

No. A person with a normal body weight should not reduce it solely because of a PCOS diagnosis. In people with higher body weight, reduction can improve some metabolic and reproductive parameters, but it should not be the only treatment goal. The benefits of a healthy way of eating and movement also appear without a change in the number on the scale.

Does insulin resistance cause fertility problems?

It can affect fertility indirectly. Hyperinsulinemia can intensify androgen production, disturb follicle maturation, and reduce the frequency of ovulation. It is not, however, the only possible cause of problems conceiving. Fertility diagnostics should also cover other factors on the side of both the woman and the partner.

Does regulating periods mean insulin resistance has disappeared?

No. Regular bleeding can appear, for example, while using hormonal contraception, but it need not indicate an improvement in insulin sensitivity. Metabolic parameters and reproductive symptoms should be assessed separately.

References

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