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Is There A Relationship Between Peripheral Neuropathy and Thyroid Health?

Published February 17 2014

Peripheral neuropathy is characterized by numbness, tingling, and/or pain, typically in the hands and feet, although these symptoms can occur in other areas of the body. There can be numerous causes of a peripheral neuropathy. Diabetes is perhaps the most common cause, although other causes can include trauma, infections, and nutrient deficiencies. And this is yet another problem which does seem to be more common in people with thyroid and autoimmune thyroid conditions.

As I just mentioned, since a peripheral neuropathy affects the nerves, then common symptoms include pain, numbness, tingling, and sometimes burning. One frequently experiences these symptoms in the toes or fingers. While most cases of peripheral neuropathy are diagnosed based on the symptoms of the patient, along with certain procedures such as vibration and monofilament testing (1) [1], electrodiagnostic tests such as nerve conduction studies and electromyelography can sometimes be very helpful. Sometimes quantitative sudomotor axon reflex testing (QSART) is used to diagnose small fiber neuropathy (2) [2].

What I’d like to do is discuss some of the common causes of peripheral neuropathy. Then at the end of the article I’ll discuss some of the things people can do to overcome this condition.

Diabetes. Diabetic peripheral neuropathy affects approximately half of patients with diabetes (3) [3]. The reason for peripheral neuropathy is because the high blood sugar levels can lead to nerve damage, which is why managing the blood sugar levels is critically important. Although pain, numbness, and tingling usually start in the toes and feet, it’s important to understand that the high blood sugar levels can affect any of the nerves in the body. For example, the nerves which control digestion can be affected by high blood sugar levels, and thus affect the digestive process. The high blood sugar levels can also lead to impotence in men and vaginal dryness in women, as well as bladder problems. Just remember that the nerves supply every tissue and cell in the body, and as a result, if someone has diabetes and doesn’t manage it well then the condition can have a profound impact on the nervous system.

Alcoholism. Chronic alcohol consumption can also lead to painful peripheral neuropathies. The mechanism behind alcoholic neuropathy is still not completely understood, but some of the possible mechanisms include activation of spinal cord microglia after chronic alcoholic consumption, oxidative stress leading to free radical damage to nerves, activation of mGlu5 receptors in the spinal cord and activation of the sympathoadrenal and hypothalamo-pituitary-adrenal (HPA) axis (4) [4]. Nutritional deficiencies (especially thiamine deficiency) and/or the direct toxic effect of alcohol have also been implicated in alcohol-induced neuropathic pain (4) [4]. Fortunately the prognosis of alcoholic peripheral neuropathy is good upon discontinued use of alcohol consumption (5) [5].

Nutrient deficiencies. I just mentioned how a deficiency in thiamin (vitamin B1) due to chronic alcohol consumption can potentially lead to a peripheral neuropathy, although I also listed a few other mechanisms which could contribute to this condition in alcoholics. I also spoke about diabetic peripheral neuropathy, but one important thing to keep in mind is that a vitamin B12 deficiency can lead to a peripheral neuropathy. And chronic use of Metformin, which is a medication commonly taken by diabetics, can lead to a vitamin B12 deficiency. And vitamin B12 deficiency is often misdiagnosed as diabetic neuropathy (6) [6] (7) [7]. So one needs to be cautious when taking any type of medication, as many medications lead to nutrient deficiencies. Since oral contraceptives can lead to deficiencies in folate and vitamin B12, taking “the Pill” can also lead to a peripheral neuropathy (8) [8]. Anticonvulsants can decrease folate and cause a peripheral neuropathy (9) [9]. While a deficiency of vitamins B1 and B12, along with folate, can lead to a peripheral neuropathy, elevated levels of vitamin B6 can actually cause a peripheral neuropathy (10) [10].

Heavy Metal Toxicities. Heavy metal exposure can also be a factor in the development of a peripheral neuropathy. There is evidence that cadmium can be a potent neurotoxicant for the peripheral nervous system and might play a role in the development of peripheral polyneuropathy (11) [11]. There is also evidence that mercury can induce a peripheral neuropathy (12) [12] (13) [13]. And the same holds true for lead (14) [14] and arsenic (15) [15] (16) [16]. What’s interesting is that some of these cases of peripheral neuropathy were caused by high doses of certain nutritional supplements and herbs. This is why one has to be careful about self-treating their condition. And quite frankly, even healthcare professionals need to be cautious about giving high doses of certain supplements and herbs.

Infections. Certain infections can cause a peripheral neuropathy. Human immunodeficiency virus (HIV) is strongly associated with peripheral neuropathies (17) [17] (18) [18]. Hepatitis C can also lead to a peripheral neuropathy (19) [19], and a few other pathogens can cause this condition as well.

Celiac Disease. Peripheral neuropathy is one of the most common neurologic manifestations associated with Celiac disease (20) [20]. Many people still think that a gluten intolerance will only result in digestive symptoms, but more research is showing that it can result in neurological symptoms. So just because you don’t have any bloating, gas, or other digestive symptoms after eating foods with gluten doesn’t mean you don’t have a gluten sensitivity problem. Of course Celiac disease doesn’t just involve an intolerance to gluten, as it is an autoimmune condition which is caused by gluten in genetically susceptible individuals. What’s interesting is that some people with Celiac disease don’t experience any overt symptoms upon consuming gluten. However, if someone has Celiac disease, eating a small amount of gluten can still cause damage to the cells of the intestines. And so it is very important for those with Celiac disease to completely eliminate gluten from their diet.

Hypothyroidism. Some people with hypothyroid conditions experience peripheral neuropathy. Unfortunately there aren’t too many studies showing a correlation between hypothyroidism and peripheral neuropathy, although one study I came across looked at 39 patients with hypothyroidism (high TSH and depressed levels of T3 and/or T4), and objective findings supporting a clinical diagnosis of polyneuropathy were present in 13 (33%) of these people (21) [21]. In most cases the polyneuropathy was mild.

Hyperthyroidism. Hyperthyroidism typically isn’t associated with peripheral neuropathy. There was a published incident of someone who developed peripheral neuropathy while taking propylthiouracil (PTU), which is a type of antithyroid medication (22) [22]. Once the person weaned off the medication the neurological symptoms disappeared.

Can Following A Natural Treatment Protocol Help?

As for whether following a natural treatment protocol can help with a peripheral neuropathy, it of course depends on what is causing the problem. For example, if the problem is due to diabetes, then the key is to effectively manage the blood sugar levels. While taking medication might be necessary in some cases, especially in type 1 diabetes, many times eating well is the key. This is especially true for type 2 diabetes, which unlike type 1 diabetes is not an autoimmune condition, and can be prevented through diet and exercise.

If someone has a nutritional deficiency then obviously this can be addressed by correcting the deficiency. As I discussed earlier, certain medications can result in deficiencies of the B vitamins (B1, folate, B12), which can lead to a peripheral neuropathy. When this is the case, having the medical doctor wean the patient off the drug and/or giving B vitamin supplementation can help with this problem. I also mentioned how high doses of vitamin B6 can potentially cause a peripheral neuropathy, and thus is something to be aware of.

With regards to heavy metals, doing things to reduce one’s exposure to heavy metals is important, along with eliminating heavy metals from the body. Everyone has heavy metals in their tissues, but two things to keep in mind are that 1) some people have more heavy metals in their body than others, and 2) some people react to very small levels of heavy metals, while others might not react to high levels of heavy metals. In other words, not everyone who has high levels of mercury, cadmium, or other heavy metals will experience a peripheral neuropathy, while some people might experience this problem even if they have low levels of these toxic metals.

If someone has a condition such as Celiac disease that is causing a peripheral neuropathy then this needs to be addressed. Avoiding gluten is essential for those who have Celiac disease, and this frequently will result in resolution of the peripheral neuropathy. One of the reasons why Celiac disease can lead to the development of peripheral neuropathy is because it causes depletion of certain nutrients, such as folate and vitamin B12 (23) [23] (24) [24].

With regards to thyroid conditions, if someone has a hypothyroid condition and a has peripheral neuropathy, then raising the thyroid hormone levels can help. Many people choose to do this by taking synthetic or natural thyroid hormone. If someone has depressed thyroid hormone levels due to Hashimoto’s Thyroiditis then taking thyroid hormone is still an option, although my goal is to address the autoimmune component of the condition. Even when this is accomplished, the person still might need to take thyroid hormone on a permanent basis. Fortunately many of the patients I work with who have Hashimoto’s Thyroiditis have thyroid hormone levels which are still within the reference range. On the other hand, some of the people I work with do have depressed levels of T3 and/or T4.

It of course is also important to rule out other causes of peripheral neuropathy in people with thyroid and autoimmune thyroid conditions. For example, if someone with Graves’ Disease or Hashimoto’s Thyroiditis also has Celiac disease and is still consuming gluten, then this could be causing a vitamin B12 deficiency, thus resulting in a peripheral neuropathy. Or if they have diabetes or are an alcoholic then these also can cause a peripheral neuropathy. And so this is why it’s important to take a proper case history.

Alpha-lipoic acid, acetyl-L-carnitine, benfotiamine, methylcobalamin, and topical capsaicin are among the most well-researched alternative options for the treatment of peripheral neuropathy (25) [25]. Other potential nutrient or botanical therapies include vitamin E, glutathione, folate, pyridoxine, biotin, myo-inositol, omega-3 and -6 fatty acids, L-arginine, L-glutamine, taurine, N-acetylcysteine, zinc, magnesium, chromium, and St. John’s Wort (25) [25]. However, while supplements can be helpful, the goal should be to find the cause of the problem if at all possible. And as I mentioned earlier, in some cases taking high doses of certain supplements can cause more harm than good, and perhaps can even cause a peripheral neuropathy.

In summary, while there is a connection between hypothyroidism and peripheral neuropathy, and a potential for PTU to cause this in some people with hyperthyroid conditions (although to be fair, this isn’t something I’ve seen with my patients), there are also other factors which can cause a peripheral neuropathy. Some other causes include other endocrine conditions such as diabetes, nutrient deficiencies, heavy metal toxicities, certain infections, chronic alcoholism, and Celiac disease can all be factors. Many times peripheral neuropathy can be helped naturally, although it does depend on the cause of the problem.