HI and welcome,

Heat intolerance is a common element of autonomic neuropathy. Since you have other symptoms (urinary retention), then it IS likely to be related. There are also common aspects of autonomic neuropathy...like orthostatic hypotension (BP drops when you stand up -- making you dizzy/lightheaded), increased heart rate, and stomach fullness, bloating, nausea from gastroparesis. Do you have any of these other problems? Do you sweat easily in the heat...or not at all.

Either way, you should consider testing for autonomic functions. A QSART is a very detailed sweat test to see how you respond to heat. If you have other symptoms I mentioned above, there are more testing options.

Do they know the cause of your polyneuropathy?