The hormone responsible for decreasing blood glucose concentration is Insulin.

Blood glucose levels are tightly regulated by several hormones to maintain homeostasis. Insulin, produced by the beta cells of the pancreas, plays a key role in lowering blood glucose levels. It promotes the uptake of glucose by cells, especially in muscle and adipose tissue, and stimulates the liver to convert glucose into glycogen for storage (glycogenesis). In contrast, other hormones such as glucagon, cortisol, and epinephrine work to increase blood glucose levels by stimulating glycogen breakdown and gluconeogenesis.

- Glucagon: Secreted by alpha cells of the pancreas, it increases blood glucose by promoting glycogenolysis.
- Cortisol: A glucocorticoid hormone that increases gluconeogenesis and decreases glucose utilization.
- Epinephrine: Released by the adrenal medulla, it rapidly raises blood glucose during stress by glycogenolysis.

Therefore, among the options, insulin is the only hormone that lowers blood glucose concentration.

Reference: Ganong’s Review of Medical Physiology, 26th Edition, Chapter 65: Endocrine Pancreas and Diabetes Mellitus