During the course of efforts to isolate GHRH from hypothalamic extracts, Krulich and McCann discovered a fraction that inhibited GH release from pituitary incubates, in vitro. They named the fact (ΓÇÿgrowth hormone release inhibitory factorΓÇÖ) and postulated that GH secretion was regulated by a dual control system, one stimulator and the other inhibitory. Relatively little attention was paid to this concept when first described since it was thought by most workers to be a non-specific effect.
