ecdysone A steroid hormone, secreted by a pair of prothoracic glands in the thorax of insects and by Y organs in crustaceans, that stimulates moulting (see ecdysis) and metamorphosis. In insects its release is stimulated by prothoracicotropic hormone. It acts on specific gene loci, stimulating the synthesis of proteins involved in these bodily changes. Some plants contain phytoecdysones, which are structurally similar to the insect ecdysones. They may help to protect the plant by interfering with the moulting cycle of insect pests that consume plant tissue.

ecdysone A hormone, produced by the prothoracid glands, which brings about moulting in an insect. The form of the animal after each moult is determined by the juvenile hormone. Ecdysone acts mainly on the epithelial cells.