Hunter Tootoo isn't the first MP to leave his party's caucus. The past few years have seen several departures. In two cases, MPs remained in caucus but took leave to seek treatment for substance abuse.

January, 2016 - Liberal MP and former CTV News journalist Seamus O'Regan took a few weeks over the holiday break to go into a "wellness" program to live an alcohol-free lifestyle. He was back on the Hill when Parliament resumed sitting on Jan. 25.

October, 2012 - New Democrat MP Romeo Saganash took leave to seek treatment for alcoholism - but remained part of caucus - after he was escorted off an Air Canada flight for being intoxicated. He returned to the House in January, 2013.

MPs who quit a caucus generally do so to join another party. But in most of the cases below, the departures happened in the wake of a controversy.

November, 2014 - Liberal MPs Massimo Pacetti and Scott Andrews were suspended from caucus, then officially kicked out a few months later, after two NDP MPs made accusations against them. Justin Trudeau did not allow either man to return to the caucus, although both denied all allegations of improper behavior.

September, 2013 - Dean Del Mastro stepped down from the Conservative caucus when he was charged with breaking election laws. He was found guilty and his first appeal was rejected. He filed a second appeal last April.

March, 2013 - Conservative cabinet minister Peter Penashue resigned his seat to seek re-election after it was revealed his campaign had broken election spending rules. He lost a subsequent byelection.

April 2012 - New Democrat MP Bruce Hyer quit his caucus to sit as an independent over being ordered to vote against ending the long-gun registry. Hyer went on to join Elizabeth May in the Green Party, doubling the size of the party’s caucus.

December, 2011 - Conservative MP Peter Goldring left the Conservative caucus after he was charged with refusing to take a breathalyzer. He was asked back to the caucus after he was found not guilty in June, 2013.

April, 2010 - Conservative minister of state for the status of women Helena Guergis was kicked out of cabinet and caucus over what then-prime minister Stephen Harper called serious allegations, which he also referred to the RCMP. Nothing came of the RCMP investigation.