Testosterone decanoate (BAN) is an androgen and anabolic steroid and a testosterone ester. It is or has been a component of Sustanon, along with testosterone propionate, testosterone phenylpropionate, and testosterone isocaproate. Testosterone decanoate has been investigated as a potential long-acting injectable male contraceptive. Testosterone decanoate (BAN) is an androgen and anabolic steroid and a testosterone ester. It is or has been a component of Sustanon, along with testosterone propionate, testosterone phenylpropionate, and testosterone isocaproate. Testosterone decanoate has been investigated as a potential long-acting injectable male contraceptive.