Castrating older mice extended lifespan most, study finds

Castration extended the lives of male mice at all ages tested, with the largest increase among animals operated on later in life, according to research reported by ERR. Independent researchers have yet to assess whether castration or drugs that mimic its effects can extend the lifespan of males.

Researchers at the University of Texas studied genetically diverse UM-HET3 mice to investigate whether substances produced by the testes affect lifespan early in life or through their long-term effects. They removed the mice’s testes at 20 days old, before puberty; at 60 days, just after puberty; or at 240 days, when male mice typically begin to experience a sharp rise in mortality.

All three groups of castrated mice had lower early mortality and lived longer than control animals. Median lifespan rose by 19.3 percent for mice castrated before puberty, by a quarter for those castrated just after puberty, and by nearly a third for those operated on at 240 days. The oldest group also lived significantly longer than mice castrated when young.

Castration reduced muscle mass and increased body fat in all groups, making the males’ body composition more similar to females’. Mice castrated at 240 days had developed muscle like intact males before surgery, but their muscle mass then fell and their fat increased to levels seen in mice castrated earlier. The researchers said this suggests the body adjusts to new hormone levels without carrying a lasting burden from earlier stages of life.

The team had initially thought that older mice lived longer because they had built up muscle and physical reserves when young. But tests of grip strength and frailty did not support that explanation: mice castrated later did not retain more strength as they aged or remain physically stronger than those operated on earlier.