Image copyright SB Nation Image caption Ryan O'Callaghan is the seventh former NFL player to have come out as gay

Former NFL player Ryan O'Callaghan has come out as gay, revealing that his anguish over his sexuality drove him to write a suicide note.

The New England Patriots and Kansas City Chiefs lineman told Outsports that fear of rejection spurred him to hide his homosexuality.

He even built a cabin near his Kansas City home and bought guns, planning to take his secret to the grave.

It is still exceedingly rare for top-flight male US athletes to come out.

The 33-year-old told Outsports, a website focused on LGBT issues in sport, that he realised he was gay while at high school in a conservative northern California town.

Image copyright SB Nation Image caption Ryan O'Callaghan (middle) as a promising NFL prospect with his family

The 6ft 7in, 330lb (149kg) hulk saw the ultra-macho world of American football as the perfect camouflage for his true identity.

"No one is going to assume the big football player is gay," he said. "It's why a football team is such a good place to hide."

A litany of sporting injuries eventually led O'Callaghan into painkiller addiction.

"It helped with the pain of the injuries, and with the pain of being gay," he told Outsports.

More on LGBT issues

Media playback is unsupported on your device Media caption The day I told my students I was gay

Most sport fans 'would welcome gay players'

YouTube changes settings after LGBT row

"I just didn't worry about being gay when I took the Vicodin."

As his NFL career waned, he began to distance himself from his family, telling himself that it would make his suicide easier for them to accept.

O'Callaghan eventually plucked up the courage to tell Kansas City Chiefs general manager Scott Pioli about his sexuality.

"I'm gay," O'Callaghan said, after asking for a meeting.

Pioli responded: "So what's the problem you wanted to talk to me about?"

O'Callaghan, who retired from the NFL in 2011, described the huge relief the revelation brought him.

"As long as there are people killing themselves because they are gay," he said, "there is a reason for people like me to share my story and try to help."

According to Outsports, O'Callaghan is the seventh former NFL player to have come out as gay.

In basketball, the NBA's Jason Collins in 2013 became the first openly gay male athlete still competing in a major US sports league.