On Monday, shares of Needham-based Parametric Technology Corp. were cut to “hold” from “buy” at Jefferies by analyst Ross Macmillan. His 12-month target price is now $21 per share, down from $25. Nevertheless, the stock advanced on Tuesday. The analyst’s downgrade says “our most recent field work points to further deterioration of demand. Many aspects of our Buy thesis . . . remain an opportunity, but weaker demand means it will be slower to realize.” For fiscal 2012, Parametric expects revenue growth of 8 to 10 percent. It reported revenue of nearly $1.17 billion in fiscal 2011.