Adrenaline, also known as epinephrine, is a catecholamine hormone produced by the adrenal medulla that plays a crucial role in the body's fight-or-flight response by increasing heart rate, bronchodilation, and glucose metabolism. In clinical practice, it is vital for managing anaphylaxis, cardiac arrest, and severe asthma attacks, as it rapidly counteracts life-threatening symptoms. A key association is its use in auto-injectors for anaphylactic reactions, highlighting its importance in emergency medicine.