I had thyroid cancer in 2019 they removed my thyroid had a radiation pill and did not have any divers out come six years later I had a tumor in my neck and had the tumor removed . I was advised by my Oncologist to have the radiation pill again and have six and half weeks of radiation just finished the treatment two weeks ago I lost all my taste and have a bad metallic taste when I eat anything and bad salty taste when there is nothing in my mouth for water I use something calld Trevi in the water and I get a slight sweetness in my mouth and helps keeping hydrated I have been able to taste slight sweetness when I try something seet but not much I was told by my Doctor it can take four to six months, I have my finger crossed I guess its a waiting game and hope he's right I hope its some help I whish your son the best.