20-Hydroxyecdysone (ecdysterone or 20E) is a naturally occurring ecdysteroid hormone which controls the ecdysis (moulting) and metamorphosis of arthropods.

A phytoecdysteroid produced by various plants, including Cyanotis vaga, Ajuga turkestanica and Rhaponticum carthamoides, its purpose is presumably to disrupt the development and reproduction of insect pests.

These hormone-producing tissues express the ecdysone receptor throughout development, possibly indicating a functional feedback mechanism.

[citation needed] In insects, an ecdysteroid is a type of steroid hormone derived from enzymatic modification of cholesterol by p450 enzymes.

[12] However, a 2019 study found significantly higher increases in muscle mass and one-repetition bench press performance in participants dosed with ecdysterone.

[14] In 2024, the Food and Drug Administration approved a study on the efficacy of BIO101 (20-hydroxyecdysone) in treating obesity, focusing on muscle strength improvement in the lower limbs.