A look at another popular way of describing PCOS: four types based on the underlying driver. The chapter explains insulin-resistant PCOS, post-pill PCOS after stopping hormonal contraception, adrenal PCOS linked to stress hormones, and inflammatory PCOS, and what sets each apart. It is clear that this framework is not officially recognised or backed by strong clinical evidence, and explains its limits, while showing how it can still help you understand your own symptoms. The module closes with guidance on using what you have learnt to seek the right support.