Figure 1: Overview of interacting physical and chemical systems.

Structures of TBA (primary component implanted into cattle), metabolites 17β-TBOH (pharmacologically active androgen), trendione, 17α-TBOH (primary product excreted to the environment) and 17α-TBOH photoproducts (5- and 12-hydroxy-17α-TBOH) that are subject to reversion under dark conditions.