The thyroid gland helps to regulate many key body functions, including the production and release of human growth hormone (HGH), Vitamin K production and regulation (Vitamin K regulates how much oxygen that blood platelets can carry), production and regulation of epinephrine (adrenaline), and to a lesser (but seemingly just as important) extent, the regulation of the mood regulating chemicals serotonin, norepinephrine, and dopamine.
2. 2C-I is a iodinated chemical structurally related to epinephrine, norepinephrine, and dopamine.
3. Iodine is the heaviest halogen available (there is one heavier, Astatine, but it is a rare, radioactive, and completely unusable atom in pharmacology).
4. Iodine has NEVER been used in any psychotropic (mood-altering) chemicals other than thyroid medications.
While many of Shulgin's chemicals employed halogens (ie. 2C-C, 2C-B, 2C-F, 2C-T-21, and also their amphetamine homologues), all of them, with the exception of 2C-I and its amphetamine homologue DOI, employ the lighter, and consequently 'friendlier' halogens fluorine, chlorine, and bromine. Even in medical pharmacology, iodine is never used outside thyroid treatments. For example Wellbutrin (bupropion) uses chlorine, and Prozac (fluoxetine) uses fluorine.
5. 2C-I has a high affinity for serotonin HT2-type receptors, and to a lesser extent norepinephrine and dopamine receptors, all of which control critical aspects in regulating mood.
Even without testing or any kind of clinical evidence, one could conclude that by introducing a chemical into the body that has a high affinity for mood-regulating receptors, contains a halogen that not only is much heavier that anything that normally enters said receptors, but also is used in the regulation of an important endocrine gland, there is going to be trouble.
Who knows what kind of long-term damage 2C-I may have on people, not only those with thyroid problems, but healthy individuals as well!? Until some clinical data exists that shows 2C-I as not being neurotoxic, I would recommend that you stay away from taking this chemical.