The Sensex at the Bombay Stock Exchange lost 180 points, or 0.9 percent, to close at 20,425, today, on profit bookingahead of the derivatives expiry. The Nifty at the National Stock Exchange fell 56 points, or 0.9 percent, to 6,059.Stock markets in Japan, China and nSingapore ended lower between 0.1 percent and 0.7 percent.