--of endocrine problems beyond those of the insulin/glucose cycle; those involving the adrenals, the thyroid, the parathyroid . . .but you don't seem to have many indications of these (at least from you've written so far--and I'm not an expert in these areas).

The low iron stores, the cholesterol, and the underweight aspect bring two other possibilites to mind, though. The first is neuropathy through hypertriglyceridemia--hereditary high levels of triglycerides that are not affected very much by diet in those with the condition. This is not a well-researched area, but there are some reports of it. The second is the possibility of neuropathy due to nutrient malabsorption--of vitamin B12, B1, B6--and this can stem from a number of factors, but you definitely should be checked for celiac/gluten sensitivity, which can ITSELF cause neuropathy through direct autoimmune cross-reactivity with nerve components. Getting some triglyceride and Vitamin D levels would also be a good idea (have you had B Vitamin levels done?).