Which hormone is primarily involved in stress response?

Cortisol is the primary hormone involved in the body's stress response. It is produced by the adrenal glands in response to signals from the hypothalamus and pituitary gland during stressful situations. When an individual encounters a stressor, whether physical or psychological, cortisol helps the body mobilize energy by increasing glucose availability, enhancing the metabolism of fats and proteins, and suppressing non-essential functions that could detract from immediate survival. This makes cortisol vital for maintaining homeostasis during stress and is often referred to as the "stress hormone."

In contrast, insulin plays a crucial role in regulating blood sugar levels, oxytocin is primarily involved in social bonding and reproduction, and melatonin is responsible for regulating sleep-wake cycles. Each of these hormones serves important functions, but they do not have a direct role in the physiological responses and adaptations required during times of stress like cortisol does.