PHEX and craniosynostosis: The gene products chosen were of particular interest to craniofacial bone development or craniosynostosis and were: Phex, Col2a1, Tnf, Dmp1, Htra1, Fgf1, Fgf2, Por, Dcn, Igf1 and Mmp9. Results suggest significant dysregulations for 9 of these gene products after 3 or 7 days of thyroxine exposure (Figure 4).