There are several interesting assertions in this abstract for example: “sex hormones elicit the transition of the developmental phase of life into the post-developmental, downhill (aging) period.”
So we start aging at puberty basically. Eunuchs do live longer, but they still age. Perhaps you need to shut down the master hormone regulator in the brain instead of downstream. The pituitary? Is thymus atrophy prevented or reduced in older dogs treated with selegiline?