This document discusses perimenopause, characterized by hormonal fluctuations leading to irregular menstrual cycles and symptoms such as hot flashes and mood changes, typically occurring in women in their 40s and lasting 2 to 10 years. It outlines the physiological changes, the role of various hormones, and potential treatments, including medications and lifestyle modifications. Overall, perimenopause is described as a natural transition rather than a disease, with mean onset around the age of 51.