Los Angeles - Bruce Jenner found filming his tell-all interview with Diane Sawyer "tough".
The 65-year-old reality star has recorded a two-hour chat with the veteran broadcaster and reportedly broke down in tears on several occasions as he discussed his decision to transition to a woman and the impact it has had on his family.
A source told HollywoodLife.com: "There are many occasions where Bruce breaks down and cries talking about his family and his transition. It's was a tough interview for Bruce to get through.''
The Keeping Up with the Kardashians star found speaking out difficult, but was put at ease by the ABC News anchor.
The source added: "Diane is one of the best interviewers on television and did a great job of getting Bruce to open up emotionally, which made for some amazing TV.
"When they do promos for the show, fans will get a glimpse of all the emotion as some of the crying will be used."
It was announced earlier this week that the interview will air as a 20/20 special on 24 April.
Insiders say the interview will see Bruce open up about why he waited until now to make the decision to transition and confirm the name he plans to use when the process is complete.
A source said: "Bruce is going to reveal all of his struggles into transition and why it took so long for him to do it in the first place.
"It's also going to go way into how the family feels about it and what measures he is taking to complete the process.
"He is also going to reveal the name he will be using when he fully transitions."