Should I Apply for US Citizenship?

I am an MD with a PhD in Molecular Biology and I have been a permanent resident of the U.S. for the past 5 years. I obtained my permanent residency status under the NIW EB-2 category, while a postdoctoral associate at a major Boston research hospital, conducting basic research in Molecular Biology. Before that time I had spent 10 years doing basic research work in various interrelated fields of Molecular Biology. Shortly after my green card was issued, my academic appointment was not renewed and I left the field of basic research to pursue a career as a freelance medical writer, which has been my occupation since. I am currently considering applying for U.S. citizenship. Given the fact that I left the field for work in which presumably my green card was issued, might I have a problem obtaining U.S. citizenship? Could it bring into question the validity of my green card, even to the point of it being revoked? If so, is there something I could do to avoid any such potential problems?