When Billy Connolly lost his train of thought during gigs earlier this year, the audience cheered on regardless, showing the near universal affection for Scotland's best-loved comedian.

They are likely to cheer louder still at upcoming gigs after he revealed he has been diagnosed with the initial symptoms of Parkinson's disease and also undergone successful surgery for prostate cancer.

Connolly, 70, nicknamed the Big Yin, intends to keep performing, with a spokesman saying the diagnosis will not "affect his ability to work". A statement on Connolly's website said he was receiving the appropriate treatment for early stage Parkinson's.

"Billy has been assured by experts that the findings will in no way inhibit or affect his ability to work, and he will soon start filming a TV series as well as undertaking an extensive theatrical tour of New Zealand in the new year," the statement said.

It was also revealed that Connolly recently underwent surgery in the US for the early stages of prostate cancer. The comic, who has progressed from a joke-cracking folk singer to a standup, presenter and film actor, reassured fans that the surgery was completely successful.

Connolly is one of about 127,000 people in the UK with Parkinson's, which is caused by a loss of brain cells that produce the chemical messenger dopamine and can result in tremors, rigidity of muscles, slowness of movement and unsteady balance.

Bouts of memory loss are a common symptom – and, in April, after losing his train of thought during a routine, Connolly told a Belfast audience: "This is fucking terrifying. I feel like I'm going out of my mind."

Connolly, who finished filming on the final film in Peter Jackson's The Hobbit franchise at the end of last year having completed a standup tour of the UK, began working as a welder in the Glasgow shipyards after leaving school at 15, but quit to become a folk singer. He was encouraged to try standup by his music manager Nat Joseph, who hoped to emulate the success of Connolly's then singing partner, Gerry Rafferty. He made his name with a string of raucous appearances on Michael Parkinson's chat show, who also revealed that he was battling prostate cancer in July.

Connolly has starred in films including the Oscar-nominated Mrs Brown alongside Judi Dench and, more recently, as a frisky retired opera singer in Dustin Hoffman's Quartet. But he is best loved for his rambling, irreverent standup. In one of his best-known routines he describes the positions that must be adopted to undergo a colonoscopy calling the prostrate "a round thing kind of like a doughnut and it's [the doctor's] job to make sure it hasn't become a bagel yet".

In January 2012, he was named the most influential British standup of all time, ahead of Morecambe & Wise and Victoria Wood, in a poll by TV channel Dave. He also topped a Channel 4 survey of The 100 greatest standups. His biography – by his New Zealand-born psychologist wife Pamela Stephenson – was a huge bestseller.

"He's the granddaddy of standup in this country," said The Guardian's comedy critic Brian Logan. "It's usually thought of as American art form.

"Billy Connolly made it ours. He's the one who proved it didn't have to be something in frilly shirts, it didn't have to be music hall redux. A person, a microphone, a sense of the ridiculous and a love of stories – that was enough.

"Comedy fans love Connolly because he's funny in his bones, democratic in his spirit. He's a bloody-minded git and he's showed us all how exciting and irreverent standup can be."

Comedians from Alan Partridge creator Armando Iannucci to standups Jason Byrne and Kevin Bridges cite him as a hero, while fellow Glaswegian comedian Janey Godley praised his ability to make the ordinary amusing. "He's my absolute hero; the reason that I became a comedian. He tells ordinary stories and he makes them funny. He doesn't have gags. He just makes stories funny. That's a really hard thing to do," she said.

She doubted Connolly's diagnosis would dampen his inimitable spirit. "He's made in Scotland, so he's made of tough stuff," she said.

Connolly has previously spoken of his desire to "grow old disgracefully", telling the Scotsman: "I think disgraceful is the way to do it. Be a nuisance, stay alive … in Britain you're encouraged to wear a cardie and have the crotch of your trousers away down at your knees – bum fainters they call it in Scotland, because if you look at it from behind it looks as if your bum's fainted."