Hi Ragtop
In regard to the iodine - neuropathy connection. If you consider what iodine deficiency can cause ie: hypothyroidism - then that may be a contributing factor.
Here's a link to a brief article about it from the Mayo Clinic.
http://www.mayoclinic.org/diseases-c...m/faq-20058489
also:
http://jnnp.bmj.com/content/68/6/750.full
If thyroid tests (particularly TSH) show borderline either high or low (and going up & down between tests) it can be a sign of not getting adequate iodine in the diet. Although as you say, in the US that shouldn't be a problem - am I right in thinking some foods are fortified with iodine?
I think it's possible for someone to be slightly within the test ranges but still have symptoms of hypo or hyper thyroidism (bit like pre-diabetes) - maybe depending on what else they have going on with their health.
I developed a 'wobbly' thyroid (my term for it), after being diagnosed with Addison's Disease (Adrenal Insufficiency). I take iodine daily as 1 tsp of kelp flakes with food. Since starting that my thyroid tests have constantly stayed within normal range . . . however the PN has continued to progress, ie: the thyroid may be only a small factor overall.
MrsD's suggestion of eliminating all supplements then starting each again individually is one way to find out. I would be cautious about taking heaps of iodine (kelp) - as you mentioned - you don't want to induce hyperthyroidism.
Hope you're managing well enough to get that Camaro of yours out of the garage soon . . . summer's on it's way . . . time for a little cruising.