Polycystic ovary syndrome (PCOS) is one of the most common health conditions that affects hormone balance in women. The exact cause of PCOS is unknown. Researchers believe that both inherited and environmental factors play a role, but no one can explain why some people develop PCOS and others don’t.

PCOS can be diagnosed at any age, though most people receive a diagnosis in their 20s or 30s, often when symptoms like infertility (difficulty or inability to become pregnant) become more noticeable. Overall, about 6 percent to 13 percent of women of reproductive age are estimated to have PCOS.

During this stage of life, signs of PCOS can become harder to ignore. This can lead many people to wonder what causes PCOS and what factors raise the risk of developing it.

Many of the risk factors for PCOS involve changes that lead to high levels of androgen (also known as the male hormone) and inflammation in the body. In this article, we’ll explore some common causes and risk factors of PCOS.

1. Family History of PCOS

PCOS often runs in families, suggesting genetics are probably a key factor. Twin studies suggest that up to 70 percent of PCOS risk may be inherited. If your mother, sister, or daughter has PCOS, you have a higher risk of also being diagnosed with PCOS.

PCOS isn’t linked to a single gene. So far, researchers have found at least 19 different genetic variations that may contribute to the conditions. These genes help regulate several important body processes, including:

• The production and regulation of hormones
• The effect of hormones on the body
• The production and use of energy in the body
• Inflammation and immune system activity

Researchers have also found that it’s not only the genes themselves but also how they interact with each other and the environment that matters. This helps explain why PCOS can look different from one person to another, even within the same family.

2. Insulin Resistance

Insulin resistance happens when your body makes insulin but doesn’t use it effectively. Insulin is a hormone that helps regulate your blood sugar by moving glucose (sugar) from your blood into your cells for energy. When your cells don’t respond to insulin the way they should due to insulin resistance, blood sugar stays high. To make up for the high blood sugar, the body raises insulin levels. This condition is known as hyperinsulinemia.

High insulin levels can affect the ovaries, causing them to make excess androgen hormones. This hormone imbalance is linked to irregular ovulation (when eggs don’t develop on schedule). It can also cause other symptoms of PCOS, such as hirsutism (excess hair growth) and acne.

Research shows that insulin resistance is very common in PCOS. Between 65 percent and 95 percent of people with PCOS have insulin resistance and hyperinsulinemia. Although insulin resistance is often linked to overweight and obesity, more than half of women with PCOS who are at a healthy weight also have insulin resistance.

Signs and symptoms of insulin resistance may include:

• Skin tags
• Discolored or velvety patches of skin on the neck, armpits, or groin
• Weight gain

If you’ve been diagnosed with PCOS, ask your healthcare provider about getting tested for other health problems. Insulin resistance increases your risk of type 2 diabetes, heart disease, high blood pressure, and obstructive sleep apnea.

3. Excess Weight

Carrying extra weight is another risk factor for PCOS. Studies show that between 38 percent and 88 percent of women with PCOS have overweight or obesity. People with excess weight are two to three times more likely to develop PCOS compared to people with a healthy weight.

The exact connection between excess weight and PCOS isn’t fully understood. However, research suggests that obesity contributes to insulin resistance and inflammation, which may influence how PCOS develops and progresses.

Obesity and Insulin Resistance

Having excess body fat is one of the main risk factors for developing insulin resistance. Fat tissue — especially around the abdomen — releases hormones and chemicals that can reduce insulin sensitivity and lead to insulin resistance. Weight gain can also worsen insulin resistance and may trigger PCOS symptoms.

Obesity and Inflammation

Obesity is linked to chronic (long-term) low-grade inflammation. Carrying excess body weight can change how white blood cells work and raise levels of inflammatory chemicals, such as C-reactive protein (CRP).

Research shows that this ongoing inflammation can push the ovaries to make more androgen hormones, which can worsen PCOS symptoms.

4. Diets High in Sugar, Calories, and Saturated Fats

Eating habits can also play a role in PCOS. Diets high in calories, sugar, and saturated fat are linked to both insulin resistance and chronic inflammation. These foods may also drive the ovaries to make more androgens. Over time, insulin resistance and inflammation from a poor diet can increase the risk of developing PCOS or make existing symptoms worse.

There isn’t one “PCOS diet” that works for everyone. But scientists agree that a healthy, balanced diet rich in fiber can help prevent weight gain and insulin resistance. That’s why healthy lifestyle changes are often among the first and most important treatment options for people with PCOS.

5. Lack of Physical Activity

Movement and physical activity help your body respond better to insulin. When you’re active, your muscles use glucose for energy, which makes your cells more sensitive to insulin. When you’re inactive, your body can become less responsive to insulin, raising the risk of insulin resistance in PCOS.

A sedentary lifestyle can also contribute to weight gain, adding to the risk of insulin resistance and PCOS. On the other hand, regular exercise has been shown to directly affect PCOS symptoms. Studies show it can help regulate menstrual cycles and ovulation in those with PCOS. This means that being inactive not only raises the risk of developing PCOS but can also make symptoms harder to manage.

6. Smoking

Several studies have found that smoking or being exposed to cigarette smoke is linked to an increased risk of developing PCOS. A 2021 study found that women who have started to smoke may increase their risk of PCOS by about 38 percent. Additionally, smoking can worsen PCOS symptoms and is linked to abnormal ovulation.

Researchers don’t fully understand how smoking may trigger PCOS. However, they believe smoking can increase inflammation. This inflammation can disrupt hormonal balance, which may lead to PCOS.

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