Which hormone is primarily involved in insect growth and development?

The hormone primarily involved in insect growth and development is ecdysone. Ecdysone is a steroid hormone that plays a crucial role in the molting process and metamorphosis of insects. It is responsible for initiating the shedding of the old exoskeleton and the growth of a new one, which is essential for the insect to develop through its life stages. Ecdysone levels increase during the preparation for molting, signaling the insect to undergo changes necessary for growth and development.

Juvenile hormone, while important for growth and development as well, functions primarily to maintain the larval characteristics during earlier stages and to prevent the insect from maturing into an adult. It works in tandem with ecdysone, but ecdysone is the direct trigger for molting and metamorphosis.

Thyroid hormone and corticosteroids do not play a role in insect physiology; they are more relevant to vertebrates and have different functions and mechanisms within those organisms. Understanding these hormonal interactions is vital for comprehending insect development and the overall life cycle of insects.