They lose their manes…
It is not that common for lions to be neutered and those that are castrated are often in captivity.
Neutered lions lose their manes because when they lose their testicles they lose the testosterone that gives them their luxuriant heads of hair. The more testosterone they have, the bigger and darker their mane. This not only signals that they are fertile and thus attracts females, but also makes them look bigger and more ferocious.
On the other hand, the larger mane of a lion makes them more easily spotted and makes it harder to hunt. The lionesses usually do the hunting but shunned lions often hunt alone or with other shunned males.
Below you can see Simba, a neutered lion at the Kansas City Zoo, who has lost his mane.
Conversely, lionesses with overproduction of testosterone often develop manes and start to roar. This is Bridget from the Oklahoma City Zoo.
It Botswana a group of 5 lionesses from the same pride all developed manes and deep roars, due to overproduction of testosterone. This could be seen as positive for the pride because it looked to competitors that there were many males protecting the pride.