IGF1 and Headache: Several biochemical and hormonal markers, including serum levels of alanine aminotransferase (ALT), free thyroxine (FT4), and IGF-I, were found to be slightly higher in the Headache group than in the Headache-free group (21.0 IU/L vs. 17.0 IU/L; 1.33 ng/dL vs. 1.25 ng/dL; and 162.0 ng/mL vs. 144.5 ng/mL, respectively).