Poststerone increases muscle fibre size partly similar to its metabolically parent compound, 20-hydroxyecdysone.

In mice, poststerone is a major in vivo metabolite of the worldwide popular anabolic food supplement 20-hydroxyecdysone (20E). Here we present the first study on this ecdysteroid in view of the in vivo anabolic effect of its parent compound, 20E in mammals. We have monitored muscle fibre type cross sectional areas (CSA) of developing rats after treatment with poststerone as we did in a previous study with 20E.