Cortisol is a steroid hormone made by the adrenal glands that regulates the stress response, sleep, blood sugar, and inflammation.

What cortisol does

Cortisol is released by the adrenal glands, which sit on top of the kidneys. Its level rises and falls with your sleep-wake rhythm across the day, usually higher in the morning and lower towards night. This hormone helps the body respond to stress, regulate blood sugar, support blood pressure, and balance inflammation. Because it plays so many roles, cortisol is often called the stress hormone, even though it is essential for many normal daily processes. The body has a feedback system that tries to keep cortisol within a suitable range, and this system is also influenced by conditions such as illness or lack of sleep.

In PCOS, cortisol is not the main cause, but ongoing stress and poor sleep can influence appetite, cravings, blood sugar patterns, and cycle regularity. These factors often overlap with the insulin resistance challenges that are common in PCOS. For that reason, looking after sleep and managing stress is seen as part of overall supportive care rather than a primary treatment. This approach can support general wellbeing, although it does not replace medical assessment and advice. You can read more about the hormonal picture on the hormones page.

Do you need a cortisol test

A cortisol test is not a routine part of diagnosing PCOS. It is only considered when a doctor suspects another condition, such as Cushing syndrome, which involves very high cortisol levels. Interpreting the test is also tricky, because cortisol changes through the day and is affected by stress, illness, and some medicines. A single value rarely tells the whole story, and the test is usually planned and read with care. So any decision about testing is best made together with a doctor.

What it means for you

Paying attention to your sleep habits and how you handle stress can support overall wellbeing, but it is not a test that confirms or rules out PCOS. Understanding cortisol’s role can also ease worry that stress alone causes PCOS. If you notice symptoms that concern you, such as irregular periods, sudden weight changes, or other unusual signs, it is worth talking to a doctor or pharmacist. They can help judge whether further checks are right for you. For the basics, see also what is PCOS.

This glossary is education, not diagnosis. For your own situation, ask a doctor or pharmacist.