Norma, you don't specify but I assume this is a LEED-NC certification?
If there is an official policy about this, I am not aware of it. I think you should be fine because the LEED certification was for the design and construction of the building, and that's not really going away. Ideally you would be enrolled in LEED-EBOM and following its requirements. If that's not the case, you could stay within the spirit of LEED by following the LEED-EBOM requirements for alterations. See the EBOM portion of this site, and relevant MR and IEQ credits, for more on that.