Lady Gaga
Singer Lady Gaga performs during day 2 of the 2017 Coachella Valley Music & Arts Festival (Weekend 2) at the Empire Polo Club on April 22, 2017 in Indio, California. Getty

Lady Gaga may be one of the biggest stars on the planet, but the singer has now revealed the true extent of her love-hate relationship with fame.

In an emotional open letter to fans ahead of the release of eagerly-awaited documentary, Gaga: Five Foot Two, the US pop star said that she finds life in the public eye "psychologically challenging".

The Born This Way hitmaker, who revealed her struggles with post-traumatic stress disorder earlier this year, wrote: "Although surreal, happy and also hard, I'm most touched that the veil behind the aura of my fame reveals that fame is not all it's cracked up to be."

"It is lonely, it is isolating, and it is very psychologically challenging because fame changes the way you're viewed by people," the 31-year-old singer, real name Stefani Germanotta, continued.

"For me, it feels very unnatural, but complicated because I know it is my destiny to be a performer."

"Yet I am so humbled by the side of fame that breeds love from the world, the voice I've been given by my fans to spread messages of empowerment and equality, the fortunate life it's brought to me and my family and how we can now give to others in need."

Gaga: Five Foot Two, already out in the US, sees the performer bare her soul like never before, openly discussing personal issues around her romantic life, health, family and fashion. She said that she hoped the project showed fans that fame is "not all it's cracked up to be".

"I found myself witnessing myself in a way I am unable to see on my own," she said of the project."I felt proud, I felt sadness, I felt empowered, I felt vulnerable... but what struck me the most was the film's authenticity in the way Chris [Moukarbel], the director, chose to show my lowest lows, my highest highs, and the close relationship with my family that I clung to fiercely while writing my album Joanne."

Her online outpouring comes after she postponed her postponed the European leg of her Joanne Tour until 2018 due to ongoing health problems. She is suffering from fibromyalgia, a debilitating condition that causes pain all over the body.