For many women, the diagnosis of PCOS happens during a relatively short medical appointment. Blood tests may show higher androgen levels such as testosterone or DHEA-S, cycles may have become irregular, or an ultrasound may show what doctors describe as polycystic ovaries. Once enough of these findings are present, the diagnosis is made, but the explanation often stops there.

This is one of the main reasons women leave their appointment feeling confused. They know they have PCOS, but they have not been told what the condition actually involves or why these changes are happening in the body.

Most doctors diagnose PCOS using what are called the Rotterdam criteria, which are the most widely accepted diagnostic guidelines. According to these criteria, PCOS can be diagnosed when two of the following three features are present:

• irregular or absent ovulation
• elevated androgens, such as testosterone or DHEA-S
• ovaries containing multiple small follicles on ultrasound

An important point many women are never told is that you do not need to have polycystic ovaries on ultrasound to be diagnosed with PCOS. A woman may have irregular ovulation and elevated androgens and still meet the diagnostic criteria even if the ovaries look normal on ultrasound. At the same time, some women may have polycystic-appearing ovaries but not have PCOS at all. This is why ultrasound findings alone are not enough to make the diagnosis.

The name polycystic ovary syndrome also creates confusion because the structures seen on ultrasound are usually not true cysts. They are small follicles, which are immature eggs that have begun the process of development but have not completed it.

To understand why these findings appear together in PCOS, it helps to look at what normally happens during a menstrual cycle. In a typical menstrual cycle, several follicles begin to develop in the ovary during the first part of the cycle. Normally one follicle becomes dominant, continues to mature, and releases an egg during ovulation. After ovulation the follicle becomes the corpus luteum, which produces progesterone and allows the second half of the menstrual cycle to occur normally.

In PCOS, ovulation often does not occur regularly because a dominant follicle does not fully develop. When this happens, the follicles that began developing earlier in the cycle do not complete the normal maturation process. Instead of one follicle maturing and releasing an egg, several follicles begin developing but stop partway through the process. They remain in the ovary as small fluid-filled sacs, which is what ultrasound detects. Over time this creates the characteristic appearance on ultrasound that doctors describe as polycystic ovaries.

Because ovulation is not occurring regularly, progesterone is not produced in the usual way, and the normal hormonal rhythm of the menstrual cycle becomes disrupted. This is why cycles often become longer, irregular, or sometimes stop altogether.

Another piece of the puzzle involves androgens. Women naturally produce small amounts of these hormones, but in PCOS the levels are often higher than usual. Testosterone is the androgen most commonly measured in blood tests.

Higher testosterone levels can affect several tissues in the body. They can influence hair follicles, which is why some women develop increased facial or body hair or notice thinning hair on the scalp. They can affect the skin, contributing to acne and increased oil production. They can also interfere with the normal hormonal signals that allow ovulation to occur.

What many women are not told is that these hormone changes often do not start in the ovaries themselves. One of the major drivers of PCOS in many women is insulin, the hormone that regulates blood sugar. When the body becomes less responsive to insulin, the pancreas produces more of it to keep blood sugar levels stable. Over time this can lead to chronically elevated insulin levels.

Higher insulin levels can stimulate the ovaries to produce more testosterone, which then interferes with ovulation and contributes to several of the symptoms associated with PCOS.

Insulin resistance is therefore a very important part of the picture for many women with PCOS, but it is not the only factor involved. Genetics, inflammation, thyroid function, and other hormonal signals in the body can also influence how the condition develops and how it presents in different women.

This is one reason PCOS can look different from one woman to another. In many women insulin resistance plays a major role, but the symptoms do not always appear in the same way. Some women mainly notice irregular or missing periods because ovulation is disrupted. Others notice weight gain or difficulty losing weight. Some experience acne or increased facial hair due to higher testosterone levels. Even though the symptoms can look different, they are often connected through the same underlying hormonal and metabolic processes.

For many women, this is the point where the diagnosis finally begins to make sense. The blood test results, the ultrasound findings, and the symptoms they have been experiencing are no longer separate pieces of information. They are different signs of the same underlying condition affecting ovulation and hormone regulation.

Once this is understood, many of the questions that felt confusing at the beginning start to become clearer. Why cycles become irregular. Why androgen levels may be higher. Why weight, skin, hair, and energy can change at the same time.

And perhaps most importantly, it becomes easier to understand where to begin looking for the underlying drivers that may be contributing to PCOS in the first place.