- Insulin is the principal hormone responsible for lowering blood glucose levels by promoting cellular uptake of glucose, particularly into muscle and adipose tissue, and by stimulating glycogenesis in the liver.
- It also inhibits hepatic gluconeogenesis and glycogenolysis, reducing endogenous glucose production.
- Unlike glucagon, cortisol, and growth hormone, which raise blood glucose, insulin directly facilitates glucose utilization and storage, thereby maintaining normal glycaemia.
- Its deficiency or resistance leads to hyperglycaemia, highlighting its critical role in glucose homeostasis.

Reference: Davidson’s Principles and Practice of Medicine, 23rd Edition, Chapter: The Endocrine System, Page 340.