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Diabetes Complications

Hypothyroidism and Diabetes

My feet were cold most of the time. Even when I wore thick woollen socks to bed my feet were often so uncomfortable that they interfered with my sleep.
Since I have diabetes, I assumed that my problem was that I had one of the most common complications of our condition, peripheral neuropathy. So I focused all the more on controlling my blood glucose level in hopes of reversing my problem some day.Good strategy in general. But worse than useless when the assumption is faulty. My problem is hypothyroidism. This means that my thyroid gland isn’t active enough in producing certain important hormones. One of the early symptoms is increased sensitivity to cold.

I also had a couple more of the early symptoms — I had a slow heart rate and my skin was dry and itchy. This is because the hypothyroidism gives me a slow metabolism, which can explain why I have such a hard time maintaining my weight loss. I can hardly eat anything without gaining weight!

But different people have different symptoms, and some people don’t have any of them. “Hypothyroidism is more common than you would believe, and millions of people are currently hypothyroid and don’t know it,” says James Norman, M.D., on EndocrineWeb.

Hypothyroidism is an endocrine condition — just like diabetes is. That fact led me to wonder if people with diabetes are more likely to have hypothyroidism than most people. Studies in fact show that it is.

“Subclinical hypothyroidism…is relatively common in patients with type 2 diabetes,” according to a recent study in Diabetes Care, a professional journal of the American Diabetes Association.

Specifically, about 5 percent of a sample of 1,310 people with diabetes attending an outpatient clinic had subclinical hypothyroidism, according to an earlier study in Diabetic Medication, a journal of the British Diabetic Association.

That earlier study suggested 16 years ago “that thyroid function should be screened annually in diabetic patients to detect asymptomatic thyroid dysfunction, which is increased in frequency in a diabetic population.” Another study last year recommended that those of us who have diabetes get “routine annual thyroid testing.”

I doubt if more than a handful of American doctors check our thyroid function. But the thyroid-stimulating hormone (TSH) blood test is as simple as the A1C tests that our doctors do routinely prescribe.

I know from experience. Until a few weeks ago I never thought to mention my cold feet to any of my doctors, and none of them ever suggested that a TSH test would be a good idea.

Not until November when I read an article by a doctor named William Davis, who has a cardiology practice in

Milwaukee, did I suspect my real problem. Dr. Davis writes that he has “been using 97.3 degrees F orally as the cutoff for confirming or uncovering thyroid dysfunction.” My oral temperature when I measured it the first thing in the morning, as he recommends, was usually lower than that.

My primary care physician immediately agreed with my request for a TSH test. A couple of days later that test confirmed that I have some hypothyroidism with a level of 4.17 mIU/l. The lab says the “reference range” — or normal level — is 0.4 to 4.50. But many people think that the high end of that range is set far too high, and my doctor says

that my level is “borderline low.” (Counter-intuitively, a high TSH level means a low thyroid function.) He prescribed a low dose of Synthroid (levothyroxine), and my feet are already warmer.

Synthroid is the most common treatment for hypothyroidism. But generics are also available. Armour Thyroid (desiccated porcine thyroid gland), which is naturally derived, is another choice. Each of these drugs has its advantages and disadvantages.

Even before getting the TSH test, however, we need to make sure that we get enough iodine. To normalize our thyroid function, “iodine is not optional,” Dr. Davis writes in a different article.

My primary care physician agrees and himself takes half of a tab daily, and now I do the same. Iodine probably is helping me, but not enough.

This month is an auspicious time for you and me to be thinking about our thyroid gland. January is “Thyroid Awareness Month,” according to the website of that name.

“Some experts estimate that as many as 59 million Americans have thyroid problems,” that site says, “and the majority of these thyroid sufferers remain undiagnosed and untreated.”

I hope that you aren’t in that large group. But if you do have hypothyroidism, you can count on controlling it to be a lot easier than controlling diabetes.

Just don’t assume like I did that all of your symptoms are a result of your diabetes. That assumption was my big mistake.

This article is based on an earlier version of my article published by HealthCentral.

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  • Brian O'Connell at

    Hi David,
    Thanks for your recent reply to my question about Byetta.
    Today I found out that my TSH is 5.01 and my Free T4 is 0.7.
    I haven’t noticed any cold sensitivity, but I live in Southern California where it rarely gets below 60 degrees.
    I have been more fatigued lately and have noticed that I am having some memory glitches among other things.
    Like everything, I always Google whatever I am wondering about with Diabetes, so I wasn’t too surprised to see your link come up.
    Best regards, Brian

    • David Mendosa at

      Yes, your TSH level is high. Are you taking Synthroid or a generic yet?



  • Sarah at

    So glad you figured this out! The symptoms of hypothyroidism can so be subtle and easy to overlook, that it’s hard to explain how much better one feels when it’s treated. My symptoms were a little more pronounced (I was wearing a winter coat in mid-July!) but it was only when I had been on thyroid meds for a while that I realized how much my energy, initiative, and alertness had also improved. Big, big difference.