(CNN) -- Comedian John Pinette was found dead in a Pittsburgh hotel room Saturday, the Allegheny County medical examiner's office said Monday.
Pinette, 50, died of natural causes stemming from "a medical history he was being treated for," the medical examiner's spokesman said. An autopsy will not be done since his personal doctor signed the death certificate.
Pinette toured the comedy club circuit for more than two decades, but he may be best known for his role in the series finale of "Seinfeld" in 1998. His character, Howie, was a carjacking victim in the last episode.
Although past addiction problems "took a toll on his body," Pinette was "clean and sober" at the end, his longtime manager Larry Schapiro said Monday.
Pinette, who once weighed 450 pounds, slimmed to 250 pounds in the past two years. His dramatic weight loss was the subject of a new comedy set he was developing that he titled "They Call Me Slim," Schapiro said.
His manager shared his opening line: "You know how they say in every fat person there's a skinny person waiting to come out? Well, mine came out, and mine was fat."
Pinette was in college working on an accounting degree when he started performing at open mic nights at Boston comedy clubs in the 1980s, Schapiro said. He was working at a bank when he was offered $100 a night to perform at a club.
"He went to work the next day but went to lunch and never came back," Schapiro said.
He had a reputation among his friends and fellow comedians as a brilliant, incredibly funny and kind man.
"He couldn't walk past a homeless person without giving them a $20," Schapiro said. "He would say, 'There but for the grace of God go I.' "
Comedians who knew and toured with Pinette expressed their condolences through Twitter.
"He was an extremely funny guy and a great human," Russell Peters said.
Bob Saget wrote, "Funny man. Kind man."
Dane Cook posted that he did a film with Pinette. "He was one of the most generous people I've ever worked with. A hilarious comedian. Sad loss."
"A headliner both on an off stage," Bill Burr said. "Such a great man. Truly inspirational."
"I was so lucky to work so many gigs with John Pinette who was as kind as he was funny," wrote Caroline Rhea. "So very sad for his family. Way too young."