CRH (Corticotropin-Releasing Hormone), secreted by the hypothalamus, stimulates the anterior pituitary to synthesise and release ACTH (Adrenocorticotropic Hormone). ACTH then acts on the adrenal cortex to stimulate cortisol production. This forms the HPA (Hypothalamic-Pituitary-Adrenal) axis, the primary stress response system. TSH is stimulated by TRH; FSH and LH by GnRH; GH by GHRH — all via separate hypothalamic hormones.