Which hormone is primarily responsible for the body's stress response?

Cortisol is the primary hormone responsible for the body's stress response, often referred to as the "stress hormone." It is produced by the adrenal glands in response to stress signals from the hypothalamus and pituitary gland through the hypothalamic-pituitary-adrenal (HPA) axis. When an individual experiences stress, cortisol plays a crucial role in preparing the body to respond to the stressful situation. It helps to regulate metabolism, suppresses the immune response, and increases blood sugar levels to provide energy for the body’s required response, often termed the "fight or flight" response.

In contrast, while adrenaline (also known as epinephrine) is involved in the acute stress response by triggering rapid physiological changes (such as increased heart rate and heightened alertness), cortisol’s effects are more prolonged, making it essential for managing stress over time. Norepinephrine also plays a role in the stress response but works primarily in conjunction with adrenaline for immediate responses rather than the longer-term effects. Insulin, on the other hand, is involved in regulating blood glucose levels and is not associated with managing stress responses. Therefore, cortisol stands out as the key hormone for facilitating the body’s overall adaptation to stress, making it the correct answer.