Bruce Jenner filming his reality show in October 2014. (JB Lacroix / GC Images)

Bruce Jenner will speak with Diane Sawyer of ABC News about the changes he is undergoing in a special that is scheduled to begin filming this week.

The evolving appearance of Jenner, the 65-year-old 1976 Olympic decathlon champion, has led to reports, most recently by Us Weekly, that the former athlete is in the midst of a “transition from male to female.” Jenner has not spoken on the matter  but has a docuseries planned for E!, which broadcasts his family’s reality show “Keeping Up With the Kardashians.” Jenner, who has been married three times and has six kids, including two with wife Kris Kardashian. He and Kris are divorcing and on Tuesday the Sawyer interview, expected to air later this spring, was reported.

Jenner’s mother, in a interview, offered no details but did say she supports him “whole-heartedly” and is as proud of him as she was of his athletic achievements.

“Right now I am more proud of him for what he’s allowing himself to do,”Esther Jenner said. “I am more proud of him now than when he stood on that podium and put the gold medal around his neck. He deserves all the respect.”

Former Olympian and reality television star Bruce Jenner has reportedly told family members that he is in the midst of a "transition from male to female," according to People magazine. (Reuters)

[Related: What’s going on with Bruce Jenner?]

Jenner was an inspiration when he won the gold and his mother expects a new generation will find him inspiring, too.

“If he can help other people with emotional problems,” she said, “then it will all be worth it. … I have never been more proud of Bruce for who he is, himself as a father, as an Olympian, a wonderful public speaker. He instills enthusiasm in people. He’s gifted.”

His Olympic performance nearly 40 years ago made him a bona fide celebrity and one of the first crossover stars with the Wheaties box and TV resume to prove it. The Daily Beast’s Robert Silverman calls it Jenner’s “first heroism” and reminds us that memories are short:

What’s been forgotten or mentioned merely as a footnote is that long before Jenner was shoehorned into the sitcom-ish role of a bumbling and feckless if well-meaning TV dad, he was considered the greatest athlete in the world—a cultural touchstone on par with LeBron James or Lionel Messi today.

After finishing 10th in the decathlon at the 1972 Olympics, Jenner embarked on a relentless training regimen in preparation for the 1976 Olympic Games in Montreal. In an interview with Chris Jones at Esquire, Jenner described his grueling regimen and laser-like focus.

“Jenner had that photograph blown up, and he put it up on the wall in his austere apartment, over his couch. Except that he didn’t center it. He pushed it off to the left, because he was saving a spot for the next photograph, the one that would be taken when he crossed the finish line in triumph in Montreal in 1976,” Jones wrote. “He trained for eight hours a day, every day, for four years, and every night, Jenner came home and looked at that empty space on his wall. ‘I stared at that hole,’ he says, ‘and knew what was going to go there.’”

In 1976, Jenner won the gold in the decathlon, finishing with a then-world record 8,616 points. The image of Jenner crossing the finish line with his arms outstretched in triumph and his long hair flapping in the breeze became iconic, plastered on the front of a box of Wheaties cereal. He met with President Gerald Ford and was on the cover of pretty much every glossy you could find, in publications as wide-ranging in subject and tone as Sports Illustrated, Tiger Beat, and Playgirl.

In the late ’70s and early ’80s, Jenner was everywhere, making appearances on Battle of the Network Stars and starring in the campy ode to all the now-laughable aspects of the disco era, Can’t Stop the Music. On the small screen, Jenner was always available for a guest spot on shows like CHiPs, The Fall Guy, Silver Spoons, and Murder, She Wrote.

Whatever the changes he is going through, he’ll be returning to TV soon to talk about them.