What causes PCOS/PMOS?

Bottom linePCOS/PMOS doesn't have a single known cause but results from interacting hormonal and metabolic factors: insulin resistance (which drives the ovaries to make more androgens), high androgens that disrupt ovulation and cause acne and excess hair, genetics (it runs in families), and low-grade inflammation. It isn't caused by anything you did; weight can worsen it, but lean people get it too, and understanding the insulin link explains why lifestyle measures and metformin help.

The exact cause of PCOS/PMOS isn't fully known, but it involves a combination of hormonal and metabolic factors, often with a genetic component.

Key factors

• Insulin resistance: very common in PCOS/PMOS. When cells respond poorly to insulin, the body makes more of it, which drives the ovaries to produce more androgens (male hormones). This is a central mechanism.
• High androgens: excess testosterone and similar hormones disrupt ovulation and cause acne and excess hair growth.
• Genetics: PCOS/PMOS often runs in families.
• Low-grade inflammation: linked to higher androgen production.

What it is not caused by

It's not caused by anything you did. Weight can worsen insulin resistance and symptoms, but lean people get PCOS/PMOS too, and the condition can make weight harder to manage - so it's not simply "caused by weight."

How the pieces connect

Insulin resistance and high androgens reinforce each other, disrupting the normal hormonal signals needed for regular ovulation. That's why irregular periods, metabolic changes, and skin/hair symptoms tend to cluster together.

Why it matters

Understanding the insulin link explains why lifestyle measures and sometimes metformin help, and why PCOS/PMOS raises the risk of type 2 diabetes.

See what is PMOS, insulin resistance in PCOS, and our PMOS article.

Femora helps you track the irregular cycles that often signal PCOS/PMOS.