He will have to see his doctor for desiccated thyroid. Be prepared for a fight or to find a new doctor. They don't make any money on desiccated thyroid, so they fight against it. This exasperating & unusual fight with doctors is detailed in the STTM bible, with tips to help you find a new doctor.
In general, he will want to chart his body temperature and adjust dosage of desiccated thyroid to maintain 98.6 degrees.