Growth hormone (GH) is secreted by the brain, and can stimulate the liver to secrete insulin-like growth factor1 (IGF1).Bones, formed from chondrocytes, elongate from terminal growth plates as animals grow.(1) A healthy, active growth plate. All the growth plates injected with GH activated.(2) GH was injected into rat growth plates in combination with IGF1 inhibitors.(3) All GH was inhibited in a rat.(4) GH injected into a rat growth plate with a liver specific IGF1 knockout.(5) GH was added onto stem cells in a dish.