What hormone is often called the 'stress hormone'?

The hormone often called the “stress hormone” is cortisol. It is a steroid glucocorticoid produced mainly by the zona fasciculata, a layer of the adrenal cortex in glands located above the kidneys.

Cortisol helps the body respond to demanding situations by making energy more available. It promotes gluconeogenesis, the production of glucose from non-carbohydrate sources, and influences blood pressure, metabolism, inflammation, and immune activity. Its release is controlled by the hypothalamic–pituitary–adrenal axis: the hypothalamus releases CRH, the pituitary releases ACTH, and ACTH stimulates the adrenal cortex.

Cortisol is not released only during emotional stress. Levels normally follow a daily rhythm, usually peaking around waking and falling toward the late evening. Exercise, illness, injury, low blood glucose, and psychological strain can all affect secretion. Chronic excess can contribute to Cushing syndrome, while inadequate production can cause adrenal insufficiency.

Adrenaline is a common wrong answer because it also rises during acute stress. Adrenaline acts rapidly, increasing heart rate and alertness; cortisol works more gradually and helps sustain the body’s energy response.