There are multiple definitions:

1. universal global threshold(English)

   • ATD, TH

2. uridine diphosphoglucuronosyl transferase(English)

   • a family of enzymes that catalyse the covalent addition of glucuronic acid to a wide range of lipophilic chemicals
   • UDPGA, UDP
   • Enzymes
   • https://doi.org….1997.tb02718.x