One group of mice had a time-release estrogen pill implanted under their skin. The other did not.
After four weeks, the estrogen-treated mice showed amazing rejuvenation. The telomerase gene was working anew, creating healthy-sized telomeres. Tissue that was degenerating weeks before was now growing once more. The spleen and brain showed increased size. The animals regained their sense of smell, lost due to premature aging. Their brains began to produce new neurons. And yes, the testes were more powerful than ever.