Ireland striker Kevin Doyle has announced his retirement from football due to "repeated headaches".
The Wexford man, 34, said that he was finishing up on medical advice.
"I will play no further part this season and will be retiring," he wrote on Twitter.
"This year it has been clear to me that heading the ball was becoming problematic and causing me to have repeated headaches.
"Two concussions this season and numerous others over the years have made this more concerning."
Doyle, who was included in Martin O'Neill's provisional squad for the final World Cup qualifying games, named on Tuesday, played 63 times for Ireland and scored 14 goals.
The former Reading and Wolves forward played a key role under then-manager Giovanni Trapattoni as Ireland qualified for Euro 2012.
Doyle, who moved to Colorado Rapids two years ago, was named as the Ireland's Player of the Year in 2010.
Statement on my retirment pic.twitter.com/3dTXdk4EXU— Kevin Doyle (@KevinDoyle1983) September 28, 2017
He added: "After consulting the experts in the field, it has been decided that to avoid the possibility of these symptoms becoming more serious and permanent, I will be hanging up my boots for good."
Doyle started his career in the League of Ireland with St Patrick's Athletic before moving to Cork City. After two years with the Leesiders he moved to Reading in 2005 and spent four years at the club.
looking forward to our battle on the golf course Kev,take down colm once and for all 👍👊🏌🏻♀️🏹— stephen hunt (@stephenhunt1010) September 28, 2017
Former Ireland team-mate Clinton Morrsion was among those to pay tribute to Doyle. He told RTÉ 2fm's Game On: "Doyler has been a great servant for Irish football but your health is more important than football.
"He’s had a very good career and I remember him first coming into the squad and I played up front with him quite a few times.
"He’s a very good striker, he works ever so hard and he loves heading the ball, that was a big part of the game so if he’s struggling to head it and getting headaches, [his] health is more important.
"It’s not like he’s young or he’s 20 or 21, he’s had a very good career so [he’s right] to go out at the top and a very good servant for Irish football.
"He has a good record. It wasn’t just the goals he scored; it was the work-rate. You ask any striker that played with him the work-rate off the ball was really good.
"He chased down defenders and it was a dream to play with him. He was a clever player and he scored goals as well."
Doyle last lined out for the Rapids on September 3.
Ireland manager Martin O'Neill heaped praise on Doyle for his professional attitude on and off the pitch, saying: "I am disappointed to hear that Kevin has had to retire from football.
"Kevin was extremely popular with all of the players in the Irish camp and he was an excellent professional, who has served his clubs and country very well during his career."
A former underage international, Doyle made his senior debut against Sweden in 2006 and had the honour of leading his country out as captain in the 1-0 friendly win over South Africa in Thomond Park in September 2009.
The former QPR and Crystal Palace frontman was part of the squad that won the Carling Nations Cup in 2011 and featured in two games at Euro 2012.
Doyle's final appearance in a green jersey was the narrow defeat to Iceland last March in Aviva Stadium. He is joint 21st in the all-time appearance charts and joint sixth in the all-time goalscoring charts.