Diabetes and Your Thyroid

Here’s another way that diabetes impacts your whole body. Thyroid hormones affect your insulin function, and insulin can affect the thyroid gland. Over 10% of Americans with diabetes (and as many as 30% of women with Type 1) have thyroid disorders.

It’s important to keep track of your thyroid. Too much or too little thyroid activity can worsen diabetes and bring on complications. You want to know what to look for and how to deal with it.


The symptoms of thyroid conditions are easy to confuse with other conditions. As a nurse, I took care of many patients who kept getting sicker for years with no useful diagnosis, until someone thought to check their thyroid. We need to be aware of thyroid symptoms. Don’t assume that everything that happens is because of diabetes.

The thyroid gland is shaped like a butterfly sitting around the windpipe in your neck. It makes two hormones, called T3 and T4, which set the speed for your metabolism. How fast your heart beats, how deeply you breathe, your body temperature, and how your body uses insulin are thyroid-related functions.

Too much thyroid hormone (“hyperthyroid”) increases insulin resistance. Too little (“hypothyroid”) raises cholesterol. Both hypo- and hyperthyroid greatly increase the risk of heart disease.

Writing on Diabetes Self-Management, endocrinologist Patricia Wu, MD, showed that thyroid problems are more common in people with diabetes than in the general population. By the way, Dr. Wu’s article is great, and I encourage you to read it.

People with Type 1 are vulnerable because both Type 1 and many thyroid problems involve the immune system. A wounded immune system can cause diabetes along with hypo- and hyperthyroid conditions.

People with Type 1 are more likely to have a hyperthyroid condition such as Graves disease. People with Type 2 are more likely to have hypothyroid, but both types of thyroid problem are seen in both types of diabetes.

Symptoms of thyroid problems
Symptoms vary with age and sex. Dr. Wu writes that in older women, hyperthyroidism can cause “hot flashes, mood swings, sweating, and weight changes, symptoms that may be confused with signs of menopause.”

Other typical symptoms of hyperthyroidism include “irritability, fast heart rate, weight loss despite increased appetite, frequent bowel movements, insomnia, decreased energy level, and shaky hands.” Notice how similar those are to some symptoms of Type 1 diabetes.

Hypothyroid has almost opposite symptoms. Writing here, nutritionist Amy Campbell, RD, CDE, listed “feeling tired, feeling cold, weight gain, depression, dry hair and skin, and constipation” as common symptoms of low thyroid.

Notice how similar these are to Type 2 symptoms. One blogger wrote that she had cold feet for a year and always thought it was diabetic neuropathy. It turned out she was hypothyroid.

Hypothyroid is described by some patients as hell, with bizarre thoughts, extreme fatigue, and insomnia. Our blogger Eric Lagergren wrote about his hypo experiences here and here. The comments sections include many valuable stories from people with diabetes and thyroid issues.

Either hypo- or hyperthyroid can cause a “goiter,” a swelling on the neck as the thyroid grows bigger. Both hypo and hyper can cause difficult pregnancies, especially with diabetes. And they can cause various other problems as well, such as osteoporosis, a condition that causes weak bones that can lead to fractures.

How do you know?
Since you can’t tell just from symptoms, it’s important to get your thyroid checked regularly by lab tests. The most-used screening test is the thyroid-stimulating hormone (TSH). TSH is the hormone your pituitary gland uses to tell the thyroid to get working. If thyroid function is low, TSH level will be high to try to pick up the pace. If the thyroid is overactive, TSH will be low, trying to slow it down.

Officially, a normal TSH level ranges from 0.4 mU/L to 4.0 mU/L (milliunits per liter.) This can be misleading, though. People can have significantly low thyroid with a TSH of 2.0–4.0. Levels in this range may already be raising your harmful lipid levels and possibly your glucose. In Europe, some people with a TSH above 2.0 may receive thyroid medication.

Managing thyroid problems
Three things known to help with thyroid: Get tested, take medicine, and eat right.

Testing. ADA guidelines say everyone with Type 2 diabetes should be checked at diagnosis and every five years afterward for TSH levels, and those with Type 1 diabetes and certain antibodies should be screened every year. I think if there are any problems such as unexplained glucose level changes or other symptoms, thyroid levels should be checked more frequently than that.

Medicine. Hypothyroid is easily treated with a replacement hormone called levothyroxine (brand names Synthroid, Levoxyl, and others). It will take some months of testing and trying different doses to get the dose right, but once you’ve got it, you’ll feel better for years, hopefully.

Levothyroxine doesn’t work for everyone, though. There are other meds such as liothyronine (Cytomel) that may work better for you.

It’s important to take your thyroid pills every day at the same time. There are medical and surgical treatments for hyperthyroid as well. You can read more about them in Dr. Wu’s article.

Diet. The right foods make a difference. The most important thyroid nutrient is iodine, which is added to most commercially-sold salt in the U.S. If you’re using alternative salts or no salt, you may want to get more iodine. Sea vegetables (seaweed) and sea animals are the best sources.

Amy Campbell adds that, “Poultry, seafood, lean meat, whole grains, onions, beans, almonds, avocados, seeds, and low-fat dairy foods may be helpful” for thyroid problems.

Fiber, iron, and calcium supplements don’t help and can block thyroid medicine from being absorbed. Schedule your thyroid medicine a couple of hours away from intake of these supplements.

Thyroid and diabetes are so closely related that some day thyroid hormones may be used as a treatment for diabetes. For now, the important thing is to be aware of your own thyroid status and get help if it’s too low or too high.

  • KC

    I was diagnosed with hypothyroid problems 3 or 4 years ago and with Type 1.5 diabetes last summer. I actually thought my thyroid problem was getting worse (extreme fatigue, worsening depression, dry hair) when instead I was already struggling with diabetes! I am glad to know more about the connection between these two conditions.

  • ibolyaP

    I complained to my doctor about unusual symptoms I was having and she didn’t really do anything because I suffer from depression. She finally checked my levels and my TSH was up and thyroid levels were down. She also wouldn’t send me to an endocrinologist either. So now I have hypothyroidism and type 2 diabetes. That is a lot to deal with.

    • J

      Does your insurance or the endo’s office require a referral? Not all plans or doctors do, so you should check. I would find another doctor if I were you. With two hormobe disorders it is ludicrous she would not refer you if you preferred. That said, you might find that a ND Oran integrative medicine practioner gives you better care than an endocrinologist would. Either way it is important you feel comfortable with your treatment plan. Good luck.


    I’ve had repeated results of elevated TSH, but my thyroid and pituitary tests come back normal and imaging show no signs of abnormality. I had a carcinoid tumor removed from my duodenum, and although carcinoids can cause all kinds of hormone abnormalities, they insis there is no sign of another tumor. My symptoms usually manifest during sleep and include racing heartbeat, sweating, nausea, abdominal pain, constipation, dizziness and severe fatigue. I also suffer from difficult to control blood pressure despite a wide variety of therapies and medications.

    • J

      Ignore the fasting insulin bit… Posting from my mobile!