The GHRH receptor on the pituitary

It docks on the GHRH receptor, a G-protein receptor on the somatotroph cells of the front pituitary. The receptor switches on Gs, adenylyl cyclase and cyclic AMP, which opens calcium channels and empties stored growth hormone into the blood. The same cAMP signal drives CREB and Pit-1, so the cell also makes new growth hormone and new somatotrophs stay healthy. It uses the body's own release machinery rather than replacing the hormone.