Hormonal Imbalance in PCOS: Hormones, Periods & Fertility in PCOS

The female hormone system is dynamic and unique. During reproductive years, women have higher levels of oestrogen and progesterone, while testosterone remains much lower.

This is why oestrogen and progesterone are often referred to as “female hormones,” and testosterone as a “male hormone” or androgen. Understanding this balance is key in PCOS, where one of the main features is hyperandrogenism—a condition where there’s too much testosterone in the body.

In PCOS, hormone levels, particularly oestrogen and testosterone, become imbalanced. A key feature of PCOS is elevated testosterone, also known as hyperandrogenism.

This hormonal imbalance disrupts the normal ratio between oestrogen and testosterone, leading to common symptoms such as Hirsutism (unwanted facial or body hair), Acne, and Alopecia (scalp hair thinning or loss). You can explore these symptoms and other characteristics of PCOS in more detail in the Understanding PCOS module.

In a typical menstrual cycle, the hormone Luteinising Hormone (LH) only rises briefly around ovulation to help release an egg. But in women with PCOS, LH levels stay consistently high throughout the cycle. This happens because the brain sends hormone signals too quickly, causing the body to make more LH and less follicle-stimulating hormone (FSH), a hormone that helps eggs grow and mature.

Too much LH causes the ovaries to produce more testosterone (a male hormone) than usual. This increase in testosterone can lead to common PCOS symptoms like acne, unwanted hair growth, and irregular periods. It also makes it harder for eggs to develop properly, which affects fertility.

Around 35% to 80% of women with PCOS also have insulin resistance. This means the body doesn’t respond properly to insulin, the hormone that helps control blood sugar levels. As a result, the body produces even more insulin to try to compensate.

Too much insulin in the blood can trigger the ovaries to make more male hormones (androgens) like testosterone. These high androgen levels are what cause many of the common PCOS symptoms, irregular periods, acne, and unwanted hair growth.

PCOS doesn’t look the same for every woman. Your hormone levels, like LH (luteinising hormone), FSH (follicle-stimulating hormone), and androgens, can vary depending on your PCOS type (phenotype), genetics, and lifestyle.

That’s why symptoms and hormone imbalances can be very different from person to person. What’s true for someone else may not be true for you.