CRH - Corticotrophin Releasing Hormone produced by hypothalamus stimulates the pituitary gland to release the ACTH which in turn produces corticosteroid hormones by adrenal glands.
The hypothalamus which is near the pituitary gland is a small region located at the base of the brain. The hypothalamus plays a crucial role in many important functions including releasing hormones, regulating body temperature, regulates hunger etc...