Which hormone is primarily associated with stress responses and is regulated by the HPA axis?

Cortisol is the hormone primarily associated with stress responses and is regulated by the hypothalamic-pituitary-adrenal (HPA) axis. When an individual perceives a stressor, the HPA axis is activated, leading to the release of corticotropin-releasing hormone (CRH) from the hypothalamus. This hormone stimulates the pituitary gland to release adrenocorticotropic hormone (ACTH), which then prompts the adrenal glands to secrete cortisol into the bloodstream.

Cortisol plays a crucial role in the body's response to stress by increasing glucose availability, suppressing non-essential functions, and modulating immune responses. Its effects help the body to manage and cope with stressors effectively, making it a key player in the stress response system.

In contrast, insulin is primarily involved in glucose metabolism, adrenaline is involved in the immediate fight-or-flight response rather than long-term stress regulation, and serotonin is more closely linked to mood regulation and well-being, rather than directly tied to the physiological responses associated with stress.