The 35-year-old Khan was outclassed by compatriot Brook from start to finish, and looked to be in dire straits before the referee stepped in to save him from any more punishment.
Khan, who won silver as a lightweight at the Athens Olympics in 2004 and is a former unified light-welterweight champion, said he was hoping to spend more time with his family.
“It’s something to think about, definitely,” Khan told reporters when he was asked about a potential retirement. “I’ve always said I never want boxing to retire me, I want to retire from boxing.
“Punishment like that sometimes in boxing, I know I showed a big heart and took some big shots today, but sometimes too much of that can be harmful in the future.
“I’ve done more than I ever expected. Maybe I peaked too early, I was at the Olympics at 17, I won the world title at 22. I’m 35 now, I’ve been in the game a very long time, I’m an old man. I want to spend time with my kids and my family.”