Yes, I'd get the thyroid checked out.
I had swelling on my thyroid that compressed the larygeal nerve and caused problems with swallowing and talking. This showed up during a radioactive isotope scan (my blood tests were pretty normal looking tho).
I'd also visit our Myasthenia Gravis site here, as some people have problems with the throat when this is beginning to manifest.
http://neurotalk.psychcentral.com/forum77.html
Chronic sinus drainage, if infected can also affect the throat. I assume you have covered this potential?
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Weezie looking at petunias 8.25.2017
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