Robert Carradine, the US actor best known for roles in Revenge of the Nerds and Lizzie McGuire, has died aged 71.

In a statement, his family said the actor took his own life after living with bipolar disorder for nearly two decades.

The Carradine family said they wanted to announce his cause of death to raise awareness of "the stigma that attaches to mental illness".

"We want people to know it, and there is no shame in it," his brother Keith told Deadline.

Lizzie McGuire star Hilary Duff led the tributes to her former on-screen father, writing on Instagram: "This one hurts. It's really hard to face this reality about an old friend."

Born on 24 March 1954, Carradine was the youngest son of John Carradine and a brother of actors David and Keith Carradine.

Encouraged by his brother David, Robert Carradine auditioned for 1972's The Cowboys, a John Wayne film that became his first screen role.

He went on to appear in and Martin Scorsese's 1973 film Mean Streets, Oscar-winning Coming Home (1978), alongside Jane Fonda, The Long Riders (1980), with Mark Hamill, The Big Red One (1980) and Quentin Tarantino's Django Unchained in 2012.

But he was best known for playing the head nerd, Lewis Skolnick, in Revenge of the Nerds - which became one of the most popular film franchises of the 1980s, and the father of Lizzie McGuire in the noughties Disney Channel series.

Paying tribute, Lizzie McGuire star Duff said: "There was so much warmth in the McGuire family and I always felt so cared for by my on-screen parents.

"I'll be forever grateful for that. I'm deeply sad to learn Bobby was suffering. My heart aches for him, his family, and everyone who loved him."

In a statement, Carradine's family announced his death "with profound sadness", adding that the US actor was a "beloved father, grandfather, uncle, and brother".

"In a world that can feel so dark, Bobby was always a beacon on light to everyone around him," they said.

"We are bereft at the loss of this beautiful soul and want to acknowledge Bobby's valiant struggle against his nearly two-decade battle with bipolar disorder.

"We hope his journey can shine a light and encourage addressing the stigma that attaches to mental illness."

The statement added: "At this time we ask for the privacy to grieve this unfathomable loss. With gratitude for your understanding and compassion."

In his own separate statement to Deadline, Carradine's brother Keith added: "It is an illness that got the best of him, and I want to celebrate him for his struggle with it, and celebrate his beautiful soul.

"He was profoundly gifted, and we will miss him every day. We will take solace in how funny he could be, how wise and utterly accepting and tolerant he was. That's who my baby brother was."