CAITLYN Jenner couldn't hide her anger when Piers Morgan made a joke about her gender transition when she appeared on his Life Stories TV show.
The reality star underwent gender reassignment last year after revealing she wanted to live as a woman in a candid interview with Vanity Fair.
The former Olympian, 68, lashed out when Morgan asked her about her physical changes and quipped that there were "certain areas we know about", The Sun reports.
Jenner told him: "You made a comment there and that's why you would get in trouble, OK? You said 'certain areas' - that, to a trans person, is disrespectful."
Morgan defended his comment much to Caitlyn's annoyance.
She told him: "It's not funny. It's life. It's a very serious part of my life.
"It's not something that you joke about. This is serious stuff. People die over these issues. It's not a joke."
Morgan, 52, then said he understood where she was coming from and replied: "Point taken."
Since revealing she was going to live as a woman, Jenner has been praised for being so open about her journey.
However she has been at war with her ex-wife Kris Jenner - who claimed she lied about certain aspects of their marriage following their split.
Morgan told her: "[Kris] has inferred pretty strongly that you mislead her, that you weren't honest with her when you got married because you had already attempted to transition once and then stopped. Is it true that you were not honest with her?"
Jenner replied: "I definitely told her. I even dressed up with her before we got married, only on one occasion.
"I had been on hormones for four-and-a-half years ... there are changes when you are on hormones which are tough to hide."
Morgan asked if she had breasts at the time and Jenner said: "Yes, so yes I was honest to that point, I'm sure I downplayed it quite a bit but I was honest with her. I told her before I ever slept with her. She knew."
Morgan then asked if Jenner sent the Kardashians an unfinished version of her memoir and she confirmed she left out "the last couple of pages where I talked about gender confirmation".
She continued: "I didn't tell anybody, Why? It's none of their business ..." before adding they had no reason to be "pi**ed off".