(Adds details, updates prices to close)
TORONTO, Dec 4 (Reuters) - Canada's benchmark stock index lost ground on Monday as energy and mining shares tracked commodity prices lower, while uranium companies bounced after Kazakhstan, the world's largest producer, slashed its uranium output forecast for the next three years.
* The Toronto Stock Exchange's S&P/TSX composite index ended the session down 69.94 points, or 0.44 percent, at 15,969.03.
* There were two decliners for every advancing stock and eight of the index's 10 main industry groups ended in the red.
* Shopify Inc, down 6.3 percent at C$122.64, was among the heaviest weights on the index. The commerce software company has lost more than 17 percent of its value since hitting a peak on Cyber Monday, when it said its merchants had sold more than $1 billion of goods over the Thanksgiving shopping weekend.
* The energy group retreated 1.7 percent, as oil prices fell with the market eyeing signs of rising U.S. production. Suncor Energy Inc fell 1.8 percent to C$43.76, as U.S. crude prices lost 1.6 percent to $57.45 a barrel, while Brent shed 2 percent to $62.45.
* The largest percentage gainer on the TSX was uranium producer Cameco Corp, which surged 12.9 percent to C$13.59, while an uranium exploration company, NexGen Energy Ltd , rose 16.5 percent to C$3.46 as the plans by Kazakhstan's state-run uranium mining company to cut production were expected to boost the price of the metal.
* The materials group, which includes precious and base metals miners and fertilizer companies, lost 1.2 percent. (Reporting by Fergal Smith, editing by G Crosse)