Caitlyn Jenner has told how winning an Olympic gold medal left her feeling "trapped" and "stuck" in her male body.

Today's huge TV reality show star and vocal activist for trans rights describes her greatest sporting achievement, competing as Bruce Jenner at the 1976 Montreal Olympics, was a moment of enormous turmoil.

She recalls thinking after her medal win: "Did you build up this person so big that you're stuck with him the rest of your life? It was scary.

"People suffering from gender dysphoria [a mismatch between someone's biological sex and their gender identity] is basically like being born right-handed or left-handed. It's just who you are. It's something I didn't understand, especially growing up in the 1950s and 60s," Jenner told the BBC's Don't Tell Me the Score podcast.

"I remember getting up the next morning [after winning] and walking to the bathroom without a stitch of clothes on. The gold medal was sitting there on the table. I put it around my neck, looked in the mirror and asked myself… 'Am I stuck with this person the rest of my life'?"

Jenner considered transitioning when she was 40 but couldn't go through with it. She then met and married Kris Kardashian, becoming step-father to Kim, Kourtney and Khloe.

She and Kris had two daughters together, Kylie and Kendall and it was only after their marriage broke down, she returned to considering transitioning. 

Jenner said: "Now things were different. What a great opportunity to make a genuine contribution to understanding in society when you're playing in the fourth quarter of life."

The 70-year-old was awarded Glamour's woman of the year in 2015, appeared on the cover of Vanity Fair and won the Arthur Ashe courage award. 

So, has transitioning or winning gold been the greatest achievement of her life?

Jenner said:  "I would have to put my identity as higher. It was tougher to do. I trained 12 years for the Olympic Games. I trained 65 years to transition in 2015.

"It was less accepted. Everyone loved the Games. A lot of people when they see you transition hate your guts. Look at the quotes on Instagram. By far that was a lot more difficult.

"Being gender dysphoric and dyslexic - that's what made me down the line. When I got into sports it became more important for me to succeed at sports and work hard at sports because of all these issues.

"I look at a lot of people who are successful and then you look back on their lives and it's 'Oh my God, this is what you were struggling with when you were younger'.

"I don't have to sneak around anymore. I don't have to have two suitcases, one for him one for her.

"I'm glad I had all those issues. They say success is not measured by heights obtained but by obstacles overcome."