My understanding is that all the natural thyroid products are desiccated, but that some are prescription and some are non-prescription. The prescription versions are concentrated and have reliable dosages, whereas the whole glandulars have been processed to remove the active components as much as possible, so that the remaining activity is low and variable.
I tried for years to bring my thyroid up without using any desiccated product, but I have failed. So far, I've been grateful for the boost I've received from nonprescription glandulars.