The Catholic Church has accepted the resignation of Calgary Bishop Fred Henry, the outspoken leader who came under fire last year for his stance on Alberta’s Gay-Straight Alliances.

In a letter dated February 6, 2016 and posted on the Calgary Diocese website on Tuesday, Henry says that he had been mulling over the decision ever since August 2013.

He cites medical reasons in the letter, saying that he suffers from a form of arthritis known as ankylosing spondylitis for which there is no cure.

"AS is also an autoimmune disease meaning that the body's immune system becomes confused and begins to "attack" the body. In AS, the joints in the spine are the target of the immune attack resulting in pain and stiffness (inflammation) in the neck and back," he wrote.

He said that the first symptoms began when he was in his early 20s but it wasn't until he ws 35 when he was officially diagnosed.

The disease, according to Henry, has progressed to the point where he couldn't turn his head properly anymore and has a permanent stoop.

He finished the letter by saying that 'someone younger with more energy, stamina and pastoral vision' should take over for him.

Henry is now 73, two years short of the mandatory retirement age for bishops.

Last January, Henry lashed out at the provincial government in a letter over the newly established LGBTQ guidelines in Alberta schools.

Henry accused the government of not consulting the Catholic community and breathing ‘pure secularism’.

In another letter, he called them anti-Catholic and totalitarian and said that gender is determined by God and should not be questioned.

Henry will be replaced by William McGrattan, who most recently served as the bishop of the Diocese of Peterborough.

His retirement was effective December 31, 2016.