Hi,
The causes of polyneuropathy other than Diabetes are- old age, some medications and drugs, such as some chemotherapy drugs,
alcohol abuse, AIDS, environmental toxins, and inherited neurological neuropathies. However no underlying cause can be found in a majority of patients. It may be the use of anticancer drugs for thyroid cancer that may have lead to the development of Polyneuropathy for you. Please consult a neurologist for evaluation, diagnosis and treatment. Hope this helps you.