GC-1 is structurally very similar to thyroid hormone T3:

                      CH3
    |                 |
    |     .     .     |
   / \   / \   / \   / \
  /   \ / _ \ /   \ / _ \             This is GC-1
       | / \ |     | / \ |
       | \_/ |     | \_/ |     .      OH
      / \   /     / \   / \   / \    /
     /   \ /     /   \ /   \ /   \  /
   HO     '   H3C     '     O     ||
                                  ||
                      I           O 
                      |
    I     .     O     |
     \   / \   / \   / \
      \ / _ \ /   \ / _ \    H2N      This is T3
       | / \ |     | / \ |     |
       | \_/ |     | \_/ |     |      OH
      / \   /     / \   / \   / \    /
     /   \ /     /   \ /   \ /   \  /
   HO     '     I     '     '     ||
                                  ||
                                  O