Years ago, I heard of a Doctor getting wonderful results using thyroid medicine with his Down Syndrome patients. He said that what made him try this approach was that he saw some of the same physical indicators in patients with low thyroid activity as in Down Syndrome patients. I remember him talking about the overly rounded face. One of the parents of a Down Syndrome child tearfully said that the thyroid medicine had changed her child.
From what we have been learning at this forum, the need for Iodine lines up with what this doctor found out.