There are three FDA-approved testosterone injection formulations for use: ТК (Тест Ципионат),ТЭ (Тест Энантин), and TU (Test undecanoate). They are both testosterone and have different half-lives because they attach to ester chains of different lengths. TU has the longest ester chain, consisting of 11 carbon atoms, so it has the longest half-life and lasts longer after injection. TC and TE …