Strength measurements did not explain longer survival after adult castration
Male mice castrated in adulthood had the longest median lifespan, but grip strength and frailty measurements did not support the hypothesis that they had built a reserve of physical strength.
Adult castration extended mouse lifespan, but strength measurements did not explain the result
In a preprint from James Nelson's group, male mice were castrated at 20 days of age, before puberty, at 60 days, after puberty, or at 240 days, in adulthood. Median lifespan was 841, 887, and 937 days, respectively. Control mice underwent surgery without removal of the testes and had a median lifespan of 705 days. The manuscript has not yet been peer reviewed.
The authors proposed that retaining the testes until 240 days helped mice build a reserve of physical strength that extended their lives. They tested this idea by measuring grip strength and counting signs of frailty. Mice castrated in adulthood did no better on either measure than mice castrated earlier. These measurements did not support the strength reserve hypothesis.
Eternal Search has a dedicated entry for grip strength. In this experiment, the researchers measured it to test a possible explanation for the lifespan differences. Together with the frailty assessment, it helps test that hypothesis, but two measures cannot establish that the groups were identical in every aspect of physical condition.
Castration at 240 days also immediately halted the rise in mortality that had begun at that age. On this basis, the authors propose that factors secreted by the testes increase mortality rapidly and must remain present to sustain that effect. The factors responsible remain unidentified. Longer lifespan alone does not establish improvement across all measures of health, and the mouse experiment does not establish an effect in humans.
To test whether these factors contribute to the effects of lifespan-extending compounds, the authors propose comparing those compounds in males with intact testes and males after castration. That comparison could help identify which compounds act through factors secreted by the testes.
Open the related Eternal Search page
Sources
[1] doi.org
[2] science.org
[3] cdc.gov
[4] doi.org
[5] doi.org
[6] doi.org
[7] doi.org
[8] doi.org
This item was selected because the experiment uses grip strength to test a specific explanation for its lifespan result, giving readers a direct reason to inspect the related Eternal Search term while keeping the preprint's limits explicit.