NEW YORK • Caitlyn Jenner has undergone genital surgery, two years after the Olympic-winning decathlete announced she had transitioned to a woman.

The 67-year-old, one of the most high-profile American transgender women, says in an upcoming memoir that she had the surgery in January. She has decided to go public "so all of you can stop staring".

"You want to know, so now you know. Which is why this is the first time, and the last time, I will ever speak of it," she wrote in leaked excerpts of her memoir The Secrets Of My Life.

The excerpts were published by RadarOnline on Monday ahead of the April 25 publication of the memoir.

Jenner announced her new identity in an April 2015 TV interview and announced her change of name from Bruce to Caitlyn in a July 2015 Vanity Fair cover shoot.

Jenner, the stepfather of reality stars Kim, Kourtney and Khloe Kardashian and father to Kylie and Kendall, later had her own TV reality show which documented her transition. According to the excerpts, she said the surgery, which is costly and complex, was successful and that she feels "not only wonderful, but liberated".

Many transgender people share her distress over being asked intrusive questions about their genitals, though most forgo gender reassignment surgery, citing the high cost.

Only 11 per cent of transgender women had their testicles removed and 12 per cent underwent vaginoplasty, according to a 2016 United States survey by the National Centre for Transgender Equality.

REUTERS