This is the most commonly used drug that targets a receptor whose N-terminal domain dimerizes to its ligand binding domain using the FXXFL motif. The un·deca·no·ate form of this drug is the only one that can be taken orally, and has a much longer duration when injected than the pro·pio·nate and en·an·thate prodrugs. This drug can be administered as monotherapy in forms such as a 1% gel or patch, according to (*) WPATH guidelines. In vivo, (10[1])a double bond is removed from this drug’s leftmost ring by the enzyme 5-alpha-reductase. Due to a feedback loop, exogenous administration (10[1])of this drug or its synthetic (-5[1])analogues in men can counterintuitively cause temporary gonadal atrophy. For 10 points, name this naturally occurring steroid hormone used in transmasculine hormone therapy. ■END■ (10[1])