Citing health concerns, John MacNaughton has stepped down from his post on TransCanada Corp.'s board of directors.

The 67-year-old has been on the energy infrastructure firm's board since 2006 and has served as chairman of the panel's governance committee since 2009. His retirement took effect Wednesday.

"On behalf of TransCanada and the board of directors, I want to thank John for his many contributions during the past seven years as a director of TransCanada," company Chairman Barry Jackson said in a statement. "We were very fortunate to benefit from the wisdom of his counsel and we wish him the very best."

A graduate of the University of Western Ontario's economics program, MacNaughton has spent his career in finance. From 1999 to 2005, he served as the founding president and CEO of the Canada Pension Plan Investment Board, a panel assembled by an act of Parliament to invest national assets. MacNaughton was president of Nesbitt Burns Inc., the investment arm of the Bank of Montreal, from 1994 to 1999.

TransCanada is the company behind the controversial Keystone XL pipeline expansion. If approved, the conduit would carry crude from Alberta's oil sands to refineries on the U.S. Gulf Coast.