Testosterone-d2 (17β-Testosterone-d2) is an isotope labelled compound of Testosterone (T155000). Testosterone is the principal hormone of the testes, produced by the interstitial cells. Major circulating androgen; converted by 5α-reductase in androgen-dependent target tissues to 5α-dehydrotestosterone which is required for normal male sexual differentiation.Testerone is a controlled substance (anabolic steroid). Androgen.