Δ1-Testosterone (Δ1-dihydrotestosterone, 17β-hydroxy-5α-androst-1-en-3-one, 1-Testo, 1-T) is an androgen and anabolic steroid that differs from testosterone by having a 1,2-double bond instead of a 4,5-double bond in its A ring. It was legally sold as a prohormone in the United States until 2005, when it was reclassified as a Schedule III drug.
A 2006 study determined that Δ1-testosterone has a high androgenic and anabolic potency even without being metabolized, so it can be characterized as a typical anabolic steroid. Δ1-Testosterone binds in a manner that is highly selective to the androgen receptor (AR) and has a high potency to stimulate AR-dependent transactivation. In vivo, an equimolar dose of 1-testosterone has the same potency to stimulate the growth of the prostate, the seminal vesicles and the androgen-sensitive levator ani muscle as the reference anabolic steroid testosterone propionate, but unlike it, Δ1-testosterone also increases liver weight.
Doping with Δ1-testosterone can be detected in urine samples using gas chromatography.
A prodrug of Δ1-testosterone is Δ1-androstenedione, which may be synthesized from stanolone acetate