I think the point is there is quite a bit clinical research showing the benefits of desiccated thyroid that modern medicine has largely ignored. Dr barnes ran a 20 year study with some 1500 patients treated with his method, he found in his group which he didn't make any dietary changes to(just desiccated thyroid), that they showed huge improvements in many significant aspects vs what should have been statistical rates of heart disease/diabetes and other major cancers, in his treated groups these conditions were nearly non existent. Which led him to conclude along with other research that improper thyroid function is at the heart of many of the major illnesses.
His explanation of hypothyroidism and heart disease is very interesting. In his research he found that as soon as societies began beating infectious diseases like tuberculosis which would have killed those in society with weak immune systems(weak thyroids), that those same people now lived long enough to have heart attacks(low thyroid). Also modern medicine with its success in preventing babies and children with weak immune systems (low thyroid) from dying as would have been the case prior in history, that these people are now given a chance to survive and grow and have kids and pass on the weak thyroid traits, not to mention modern environmental toxins that add to hindered thyroid function.
I know dr. brownstein for example uses both Iodine treatment and desiccated thyroid to treat many of his hypothyroid patients.