Trenbolone Enanthate is a 19-nortestosterone (19-nor) anabolic androgenic steroid. The 19-nor label refers to a structural change of the testosterone hormone in that it lacks a carbon atom at the 19th position. The Trenbolone hormone is the Nandrolone hormone with an added double bond at carbons 9 and 11. This structural change slows its metabolism, greatly increases its binding affinity to the androgen receptor and inhibits it from aromatizing. While this is truly a slight modification, it truly creates a different hormone and one that is far more powerful than Nandrolone.