He said he took the estrogen, saying women do not know 'how lucky they are that they can be themselves'.
However, fear drove him to stop the process and he continued giving motivational speeches as a man. But he admitted he would go back to his hotel after each event, take off his suit, and dress as 'her'.
"I'd literally go up into the hotel room, change into women's clothes, and walk around," he said.
"I felt like a liar," he told ABC, reflecting on the speeches he gave, telling people to "find the champion inside you" while wearing a suit.
The first glimpse of what Bruce would look like as a woman came in 1981 during a Bob Hope special. He wore a dress, a wig and full make-up to spoof the Mandrell sisters with professional football player Merlin Olson.
By then he had already been wearing dresses and the changes were hitting his family.
Both his first and second wives knew about his secret, he revealed, admitting the revelations had put a strain on their relationships.
"Chrystie was the first one to know," he said of his first wife, Chrystie Crownover. "I said these are my issues, this is what I deal with." She was loving, he said, but fundamentally believed she could change him. Linda Thompson, his second wife, knew it was something deeper, he said.
His eldest son Burt, 36, told Sawyer about a traumatizing experience in junior high school after learning about something called a "gender struggle". Immediately he thought his father may be going through the process.
He said: "I just remember one day being in junior high class and having to kinda get up and run out of the room quickly because I was afraid that my dad was going to transition to a woman and I was never going to see him again."
Despite his choices, Bruce said was concerned his lifestyle put him at odds with the Bible. He admitted to Diane he was a Christian - citing a passage from the book of Deuteronomy, which classifies a man dressing as a woman as sin.
"'I would sit in church and always wonder, "In God's eyes, how does he see me?" he said. "Maybe this is my cause in life. This is why God put me on this earth... to deal with this issue."
Read more:
•Bruce Jenner's long-awaited interview: 'I am a woman'
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•Jamie Foxx's 'transphobic' Bruce Jenner joke
As for Kris, Bruce revealed that his third wife knew about his internal torment from the moment they started dating in the early 1990s.
She saw him cross-dressing, he revealed, but he found it difficult to fully express how deep his feelings sat; that he believed his soul to be female.
As the tell-all aired his second wife, Linda Thompson, published a blog detailing their love affair, idyllic marriage and the gender dysphoria revelations that led to their divorce after two sons and a seemingly perfect Malibu life.
Thompson, now 64, met Bruce at the Playboy mansion when he was separated from his first wife, Chrystie Crownover, the mother of his two eldest children. They fell in love and got married in Hawaii when she was already pregnant with their son Brandon.
A few years later they welcomed a second son together, Brody.
Bruce was travelling the world doing paid appearances and lived a glamorous life in Malibu, frequently seeing his elder son, Burt, and daughter, Casey, from his first marriage.
But when Brody was 18 months old and Brandon was three, Bruce revealed to Linda the secret that he finally told the world Friday night.
- Daily Mail