Anna 'Patty Duke' Pearce, Oscar-Winning Actress, Dies at 69

Anna "Patty Duke" Pearce died on Tuesday morning at the age of 69.

"This morning, our beloved wife, mother, matriarch, and the exquisite artist, humanitarian, and champion of mental health, Anna 'Patty Duke' Pearce, closed her eyes, quieted her pain and ascended to a beautiful place," her family said in a statement to ET. "We celebrate the infinite love and compassion she shared through her work and throughout her life."

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Actor Sean Astin, Duke's 45-year-old son, also paid tribute to his mother with a photo of her from a young age. "I love you mom," he captioned the image along with the family's statement.

A rep for the actress tells ET that the cause of death was from sepsis due to a ruptured intestine.

Duke, born in Queens, New York, in 1946, is known for her roles in both TV and film. At age 16, she earned an Oscar for her supporting work as Helen Keller in the 1962 film, The Miracle Worker, a role she first portrayed at age 12 on Broadway. From there, she went on to star in her own sitcom, The Patty Duke Show,   from 1963-1966. In 1967, she took on a more mature part as Neely O'Hara in Valley of the Dolls, and by 1985, she was elected president of the Screen Actors Guild, a post she kept until 1988.

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In 1982, Duke was diagnosed with bipolar disorder, and became an advocate for educating others on mental health issues. Being one of the first celebrities to come forward about her bipolar disorder, Duke lobbied before the United States Congress, and joined forces with the National Institute of Mental Health and National Alliance on Mental Illness.

Duke married her fourth husband, drill sergeant Michael Pearce, in 1986 while he was serving as a consultant on set of her TV movie, A Time to Triumph.

Up until a few weeks ago, Duke was still tweeting to her 23,000 followers. "Hi tweethearts and FB friends," she wrote on March 1. "I have been absent, but not far, believe me. I love and miss you all. Hopefully back more soon and often."

Duke's final tweet was on March 15, her wedding anniversary. "Thirty years ago today, Mike and I married," she tweeted. "We [are] having a very happy and quiet day. Love and hugs to all."

The actress is survived by her husband, three children (Sean Astin, Mackenzie Astin and Kevin Pearce), and three granddaughters.