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 (15[1])prodrugs. This drug can be administered as monotherapy in forms such as a 1% gel or patch, according to (-5[1])(*) WPATH guidelines. In vivo, (10[2])a double bond is removed from this drug’s leftmost ring by the enzyme 5-alpha-reductase. (-5[1])Due to (10[1])a feedback (10[1])loop, exogenous (10[1])administration (10[1])of this drug (10[1])or its synthetic (-5[1])analogues in men can counterintuitively (-5[1])cause temporary gonadal (10[1])atrophy. (10[1])For 10 points, name this naturally (10[2])occurring steroid hormone used in (10[1])transmasculine (10[1])hormone therapy. ■END■ (10[3])