Dear Linda:
Sorry to hear about your problems. The general answer to your question is yes, thyroid can effect bone density, nerve paresthesias, body metabolism, etc. An enlarged thyroid is something that your general care physician should take a look into. Only the neurosurgeon can accurately tell you about your lower extremity pain as he/she knows which nerves were affected. Without knowing what the presurgical exam was like, the MRI of the lower spine, etc. I really can't do justice to tell you what is going on. It may be that you have another disc problem higher up in the spinal column, but a simple MRI of the cervical spine would rule this in or out as a contributor of the upper body pain.
A pain specialist, help find the correct medication to relieve as much pain as possible. They also help in finding the correct other modalities that an individual patient needs to combat pain. This may entail biofeedback, relaxation techniques, etc. I would also recommend a rehab specialist to help with specific exercises to strengthened areas of the body to help with relieveing abnormal muscle stress due to the injury.
I hope you can find relief for your problem.
Sincerely,
CCF Neuro MD