Cortisol

The body’s main stress hormone, released by the adrenal glands.

Cortisol is a hormone your adrenal glands release as part of the stress response. It’s not a villain — it follows a daily rhythm (highest in the morning to get you going, lowest at night) and helps mobilize energy under demand. The trouble is chronic elevation: when stress never fully switches off, sustained high cortisol is linked to disrupted sleep, blunted recovery, and worn-down health. This is why recovery matters as much as load: it’s what lets cortisol come back down.