What about hypoT causes these syndromes?
The hypoT causes a buildup of muccopolysaccharide in the "tunnels" that puts pressure on the nerve. Once optimally treated, the buildup clears and the syndrome resolves... That is... it will resolve as long as the hypoT is definitely the source. Sometimes things go wrong that cannot be blamed on a faulty thyroid, and sometimes we're a little slow to look for other causes.
I haven't had carpal (or any other) tunnel problems, but I had chronic trouble with tendinitis, which I don't have any more. This happens because muscles get weaker, resulting in overstress of the tendons.