Endocrine Pharmacology USMLE Step 1 Practice Question

A 68-year-old man with a 3-year history of metastatic prostate adenocarcinoma presents to his oncology clinic for follow-up after recent bone scan revealing new lytic lesions in the lumbar vertebrae and pelvis. His PSA has risen to 187 ng/mL from a baseline of 42 ng/mL six months ago, and serum testosterone is 480 ng/dL. Vital signs show BP 152/88 mmHg, HR 92 bpm, RR 16, and temperature 37.2°C. Digital rectal exam reveals a hard, nodular, fixed prostate. The oncologist initiates continuous GnRH analog therapy and counsels the patient that an initial testosterone surge may transiently worsen his existing lower back pain and fatigue before sustained pituitary downregulation and gonadotropin suppression are achieved over approximately two to four weeks. He denies urinary obstruction symptoms, hematuria, or neurological deficits. Which GnRH analog was most likely prescribed to achieve sustained testosterone suppression?