Patty Duke, an Oscar-winning actress renowned at midcentury as a child star of stage, film and television, who, amid public struggles with bipolar disorder, went on to cultivate a respected career in adulthood as an actress and mental-health advocate, died on Tuesday at a hospital near her home in Coeur d’Alene, Idaho. She was 69.

The cause was complications of a ruptured intestine that Ms. Duke suffered on Thursday, said her husband, Michael Pearce.

Ms. Duke came to wide public notice in 1959, at 12, when she starred as Helen Keller in the original Broadway production of William Gibson’s drama “The Miracle Worker.” Anne Bancroft played Helen’s teacher, Annie Sullivan.

For her performance in the 1962 Hollywood film adaptation, in which she and Ms. Bancroft reprised their roles, Ms. Duke won the Academy Award for best supporting actress.