Interesting, I wonder if it's linked with thyroid hormones. In culture, that would seem odd, unless it's binding to receptors in a manner that hormones would, or competing with hormones in the growth serum?
I'm beginning to think the thyroid hormones are just a storage mechanism for iodine. The hormones T1, T2, T3, and T4 are actually named for the number of Iodine atoms in the molecule.
I'm only a make-believe biologist.