A lot of hypos have this problem. I have known people that were singers unable to sing any more due to hypo. Constantly having to clear your throat because of the phlegm is another throat-related hypo symptom.
Long before I was diagnosed, I went to an ENT and said : I cough a lot, I loose my voice from time to time - sometimes in mid-sentence - I have a sore throat and trouble swallowing due to the feeling of a lump in my throat; also my voice has changed. All these are classic hypo symptoms, but he didn't know that.
He stuck a tube up my nose and down into my throat - took two weeks to recover from that! - and annouced that there was absolutely nothing wrong with me! (Where have I heard that before!?!)
It seems strange to me that someone whose speciality is the throat doesn't know that the thyroid is right next door to it, and what low thyroid can do to his special area, but he didn't.
I don't have those symptoms anymore, since I've been treated for hypo - except the cough, and nothing, it seems, can get rid of that!