The Sensex lost 156 points, or 0.49 per cent, to 31,106 in early trade today. The gauge had gained 49 points in the previous session on Friday. National Stock Exchange's Nifty retreated by 45 points, or 0.46 per cent,to 9,623.The rupee depreciated 15 paise to 64 rupees and 39 paise against the US dollar in early session.