When I first started going hypothyroid, my voice deepened dramatically.  I
sounded like Froggy!  On medication, it's better, but still not normal for
me.  I suppose when I finally get the correct dose, my voice will be
completely normal.  Also, I noticed that I lost my singing voice when my
thyroid function was very low.  I had days when I could barely swallow!  I
just kept trying to clear my throat, but nothing helped.  Some days if felt
like hot liquid running down my throat.  Some days it just felt like I'd
swallowed a chicken bone.  Most of that has gone away, now that my tsh is in
the "normal" range.

My understanding is that all of this is quite common with hypothyroidism.
 Hang in there, your voice will likely come back.

Best,

Cherise