Today's Scotland on Sunday reports that his decision to retire was taken after talks with new head coach Matt Williams.
Williams is due to name a pre-Six Nations training squad and, while he is known to be an admirer of Glenn, has decided that, at 33, he is not a long-term fixture in the international set-up.
Glenn came to Scotland in 1996 after playing for Waikato in New Zealand's National Provincial Championship, joining Glasgow Accies before they merged with GHK to form Glasgow Hawks a year later. Glenn made an immediate impact at the club, which also boasted ex-Glasgow man Tommy Hayes at stand-off. Together, they were part of the outstanding Hawks team that lifted the Second Division title and the Scottish Cup in 1998 and also beat Toulouse.
Surprisingly, given that Glenn was the most exciting Scottish full-back of recent years, he ended up at No.15 by accident, being moved there in an emergency for a cup tie against Cumbernauld. Thanks to his Glasgow-born grandmother, he qualified for Scotland under the grandparent rule, and after a place in the Scotland A team against Wales, he was brought into the full international set-up and eventually won 40 caps for Scotland.
"If Glenn is hanging up his international boots it would definitely be our gain and Scotland's loss," said Glasgow backs coach Sean Lineen. "He may be getting on in years, but he still has an awful lot to offer and we can only benefit from his increased presence.
"Like me, he came to Scotland with no aspirations to play international rugby for his adopted country, but no-one has been more committed to the cause. His contribution has been immense.
"There is no doubt that his greatest moment came back in 1999 when he was outstanding in the Scotland victory over France in Paris that set up the Five Nations triumph."