PCOS Explained
Understanding Polycystic Ovary Syndrome: What It Is, Why It Happens and How It Affects Your Body
Introduction
Being told you have Polycystic Ovary Syndrome (PCOS) can leave you with more questions than answers. You may have searched online only to find conflicting information, frightening statistics or advice that doesn't seem to apply to you.
Perhaps you're wondering why your periods have always been irregular, why you're struggling to become pregnant, why you've suddenly developed acne as an adult or why losing weight seems harder than it should be. Maybe you've been told you have PCOS despite not having cysts on your ovaries, leaving you questioning whether the diagnosis is even correct.
If any of that sounds familiar, you're not alone.
PCOS is one of the most common hormonal conditions affecting women of reproductive age, yet it remains one of the most misunderstood. Despite affecting millions of women worldwide, many spend years trying to understand what it actually is and how it affects their body.
The good news is that although PCOS is a lifelong condition, it is manageable. Many women with PCOS lead healthy lives, have successful pregnancies and significantly improve their symptoms with the right support and treatment.
This guide explains what PCOS is, why it develops, how it affects your hormones and why no two women experience it in exactly the same way.
Quick Summary
PCOS (Polycystic Ovary Syndrome) is a common hormonal condition affecting around 1 in 10 women of reproductive age.
It affects how the ovaries function and can influence ovulation, fertility, metabolism and hormone production.
Despite its name, not everyone with PCOS has polycystic ovaries, and the small "cysts" seen on ultrasound are actually immature follicles rather than true cysts.
Symptoms vary widely and may include irregular periods, acne, excess hair growth, thinning hair, weight gain and difficulty becoming pregnant.
PCOS is associated with insulin resistance in many, but not all, women.
There is currently no cure, but effective treatments are available to manage symptoms and reduce long-term health risks.
Why Understanding PCOS Matters
One of the most frustrating things about PCOS is that it doesn't look the same in everyone.
One woman may have regular periods but struggle with severe acne. Another may have no skin problems at all but only menstruate three or four times a year. Some women are overweight, while others are naturally slim. Some conceive naturally without difficulty, while others need fertility treatment.
This variation means that many women don't recognise their symptoms as being connected. Some spend years treating individual problems—such as acne or irregular periods—without realising they all stem from the same underlying condition.
Understanding what is happening inside your body is the first step towards taking control of your health.
What is PCOS?
Polycystic Ovary Syndrome is a complex condition involving several body systems, including the reproductive system, hormones and metabolism.
To understand PCOS, it helps to imagine your hormones as a carefully coordinated conversation.
Every month, your brain sends chemical messages to your ovaries telling them when to grow an egg, when to release it and when to prepare the body for pregnancy. Each hormone has its own role, and when everything works well, these messages are passed back and forth with remarkable precision.
In PCOS, that conversation becomes disrupted.
Some hormones are produced in higher amounts than normal, others become out of balance, and the ovaries no longer receive the clear instructions they need to complete their monthly cycle.
The result is that ovulation may become irregular or stop altogether, leading to many of the symptoms associated with PCOS.
Why the Name is Misleading
One of the biggest sources of confusion is the name itself.
Many women assume that PCOS simply means having cysts on the ovaries.
In reality, this isn't true.
The condition was first described in 1935 by American gynaecologists Dr Irving Stein and Dr Michael Leventhal, who noticed that several women experiencing infertility also had enlarged ovaries containing many small fluid-filled structures. These structures were believed to be cysts, leading to the name Polycystic Ovary Syndrome.
Modern ultrasound technology has since shown that these are not true ovarian cysts.
Instead, they are small immature follicles, each containing an egg that started to develop but failed to reach maturity.
This is why:
You can have PCOS without having polycystic ovaries.
You can have polycystic-looking ovaries without having PCOS.
Doctors do not diagnose PCOS based on an ultrasound scan alone.
Many experts believe the condition would be less confusing if it had a different name, but for now, "PCOS" remains the internationally recognised term.
How Your Ovaries Normally Work
Before understanding what goes wrong in PCOS, it's helpful to understand what happens during a normal menstrual cycle.
Each month, your brain and ovaries work together to prepare for the possibility of pregnancy.
At the beginning of the menstrual cycle, the brain releases a hormone called Follicle Stimulating Hormone (FSH).
FSH encourages a group of tiny follicles within the ovaries to begin growing. Each follicle contains an immature egg.
Although several follicles begin to develop, only one usually becomes dominant.
As this follicle grows, it produces increasing amounts of oestrogen. Rising oestrogen levels signal to the brain that the egg is almost ready.
The brain then releases a surge of another hormone called Luteinising Hormone (LH).
This LH surge triggers ovulation—the release of the mature egg from the ovary.
After ovulation, the empty follicle transforms into the corpus luteum, which produces progesterone. Progesterone prepares the lining of the womb for pregnancy.
If pregnancy does not occur, hormone levels fall, the uterine lining sheds and menstruation begins. The cycle then starts again.
It's an elegant system, with hormones working together like members of an orchestra, each playing its part at exactly the right time.
What Happens in PCOS?
In PCOS, this finely balanced system becomes disrupted.
Instead of one follicle maturing fully and releasing an egg, many follicles begin developing but fail to complete the process.
These immature follicles remain within the ovary, creating the appearance often described as a "string of pearls" on ultrasound scans.
Because ovulation often doesn't occur, progesterone levels remain lower than expected, which contributes to irregular or absent periods.
At the same time, other hormonal changes begin to affect the rest of the body.
Many women produce higher levels of androgens (often referred to as "male hormones"), even though these hormones are naturally present in women too.
These higher androgen levels contribute to symptoms such as acne, excess facial or body hair and thinning hair on the scalp.
For many women, insulin also plays a major role.
Instead of responding normally to insulin, the body's cells become less sensitive to it—a condition known as insulin resistance. To compensate, the pancreas produces more insulin.
Unfortunately, high insulin levels don't just affect blood sugar. They also stimulate the ovaries to produce more androgens, further disrupting ovulation and creating a cycle that can be difficult to break.
The Hormones Behind PCOS
One of the reasons PCOS can seem so complicated is that it isn't caused by a single hormone. Instead, several hormones interact with one another, influencing everything from ovulation to skin health and metabolism.
In the next section, we'll explore each of these hormones—FSH, LH, insulin, testosterone, oestrogen, progesterone and AMH—in plain English, explaining what each one normally does and how changes in their levels contribute to the symptoms of PCOS.