The single source provided, a transcript from a YouTube video titled "Misconceptions About Glucose: Hormonal Regulation of Plasma Glucose @Metabolism Made Easy," provides an overview of glucose's essential role for specific tissues like the brain and red blood cells, which rely on it for energy. It clarifies that glucose itself is not harmful; rather, the associated health risks stem from elevated plasma glucose levels, which can lead to conditions such as obesity and Type 2 diabetes. The transcript explains that blood glucose is normally maintained within a tight range (80-100 mg/dL) through the actions of four key hormones: insulin, glucagon, epinephrine, and cortisol. Insulin lowers blood glucose after a meal by promoting tissue uptake and storage, while the other three hormones raise blood glucose during fasting by stimulating the liver to release stored glucose or synthesize new glucose. The overall message is to distinguish between the necessary tissue requirement for glucose and the dangers of sustained high blood sugar.