The role of insulin resistance in PCOS and fertility
Originally written by Zita West. Updated by femme using current international PCOS guidance.
Insulin resistance is an important part of PCOS biology for many people, and PCOS is associated with an increased risk of impaired glucose tolerance and type 2 diabetes. It is not, however, something that should be diagnosed from symptoms or a single fasting insulin number.
What is insulin resistance?
Insulin helps move glucose from the blood into cells. With insulin resistance, tissues respond less effectively to insulin, so the body may produce more to maintain glucose levels. In PCOS, higher insulin levels can interact with ovarian androgen production and ovulation.
How is PCOS diagnosed?
PCOS diagnosis is based on features such as irregular or absent ovulation, clinical or biochemical hyperandrogenism and polycystic ovarian morphology, while excluding other possible causes. It does not routinely require laparoscopy.
Current guidance also makes an important distinction: insulin resistance is part of PCOS pathophysiology, but clinically available insulin assays have limited value and are not recommended for routine care.
How should glucose risk be assessed?
The 2023 international guideline recommends a 75g oral glucose tolerance test (OGTT) as the most accurate way to assess glycaemic status in PCOS, regardless of BMI. If an OGTT cannot be performed, fasting glucose and/or HbA1c can be considered, although they are less accurate.
An OGTT should also be considered when planning pregnancy or seeking fertility treatment because PCOS increases the risk of hyperglycaemia in pregnancy.
Managing metabolic health
Lifestyle
Healthy eating, regular activity, sleep and sustainable weight management where appropriate can support metabolic health. Benefits apply even without weight loss.
Metformin
Metformin can be used for metabolic features of PCOS and lowers blood glucose by improving how the body responds to insulin. Whether it is appropriate depends on the individual's symptoms, risk factors and treatment goals.
Inositol
Inositol may be considered by some people with PCOS, but current guidance describes limited clinical benefits and does not support a specific type or dose as clearly superior.
Fertility treatment
If PCOS is causing anovulatory infertility, ovulation-induction treatment may be needed. Improving metabolic health can support care, but insulin resistance is not the only fertility factor to consider.
Why this matters for fertility
Insulin resistance can contribute to the hormonal environment associated with irregular ovulation. Addressing metabolic risk is therefore an important part of PCOS care, but it does not automatically restore fertility or rule out other causes of difficulty conceiving.
The bottom line
Insulin resistance is closely linked with PCOS, but routine fasting insulin testing is not the recommended way to assess health risk. Focus on appropriate glucose testing, long-term metabolic health and evidence-based fertility treatment where needed.
Further information
2023 International Evidence-based PCOS Guideline
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