As part of the endocrine system, your thyroid plays a vital role in helping to regulate and maintain balance in your blood glucose level. Thyroid disease is more common in people with diabetes. The reverse is also true: diabetes is more common in people with thyroid disease. Let’s explore the connection between these two endocrine conditions.
Glucose is a form of sugar that provides energy. You get glucose from food, and your liver also makes and stores glucose. Your pancreas produces insulin and the job of insulin is to move glucose into your cells, lowering your blood sugar level. The term diabetes refers to a dysfunction in the production or use of insulin in the body.
When your body is unable to produce insulin (type 1 diabetes), doesn’t produce enough insulin (type 2 diabetes), or fails to respond to your insulin (type 2 diabetes), excess glucose (sugar) builds up in your bloodstream. This condition, known as hyperglycemia, has numerous serious health implications and can ultimately be fatal.
The signs and symptoms of both type 1 and type 2 diabetes can develop over time or appear quickly and may include:
- Increased thirst and dry mouth
- Frequent urination
- Extreme hunger
- Irritability, anxiety, and mood changes
- Weakness and fatigue
- Blurred vision
- Dry, itchy skin
- Wounds that are slow to heal
- Numbness, tingling in feet and hands
- Erectile dysfunction or impotence in men
Unintended weight loss is a common symptom of type 1 diabetes and in some cases of type 2. Weight gain or difficulty losing weight are more commonly seen in type 2 diabetes.
Tests to diagnose diabetes include:
- Fasting glucose — a level above 120 is considered evidence of type diabetes.
- Glycated hemoglobin, also known as the HA1C test, which gives an average blood sugar over several months. A level above 6.5 is indicative of diabetes.
Doctors also typically run tests to evaluate antibodies as a way to differentiate between type 1 and type 2. These tests include:
- C-Peptide, which helps to show how much insulin is being produced. Low levels suggest type 1 diabetes.
- Glutamic Acid Decarboxylase Autoantibodies (GADA or Anti-GAD), which measures antibodies against a pancreatic enzyme. Elevated GADA is indicative of type 1 diabetes.
Type 1 diabetes
In type 1 diabetes — also known as juvenile diabetes — your immune system attacks the cells in your pancreas that produce insulin, making you unable to produce insulin. The cause of the immune attack is not specifically known, but experts believe that genetics, viruses, and environmental exposures each play a role.
- The risk factors for type 1 diabetes include:
- gender: females are at higher risk than males
- having a parent, sibling, or child with type 1 diabetes
- having another autoimmune disease yourself, including Hashimoto’s thyroiditis and Graves’ disease
- having a parent, sibling, or child with another autoimmune disease
- being geographically located further away from the equator
Type 1 diabetes is most often diagnosed in children or teenagers. There is, however, an increase in the diagnosis of type 1 diabetes in adults. This is known as Latent Autoimmune Diabetes in Adults, or LADA.
The treatment for type 1 diabetes includes:
- insulin therapy by injection
- monitoring your carbohydrate intake
- frequent testing of your blood sugar
- eating a healthy diet
- regular exercise
- maintaining a healthy body weight
Type 2 diabetes
Type 2 diabetes is not autoimmune. It develops in response to diet, lack of exercise, body weight, and other factors. In type 2 diabetes, two different mechanisms can occur:
- Your pancreas becomes unable to release enough insulin to handle sugar in your diet.
- You release insulin but your cells don’t respond to it — a condition known as insulin resistance.
Type 2 diabetes risk factors
Key risk factors for type 2 diabetes include:
- having an elevated thyroid stimulating hormone (TSH) level
- a diagnosis of subclinical hypothyroidism or hypothyroidism
- being overweight or obese
- having a high percentage of body fat, especially abdominal fat
- lack of exercise and regular activity
- family history of type 2 diabetes
- age (over 45)
- history of gestational diabetes
- history of polycystic ovarian syndrome (PCOs)
African-Americans, Hispanics, Native Americans, and Asian-Americans are also at higher risk of type 2 diabetes compared to Caucasians.
Type 2 diabetes is treated with a variety of approaches that can include:
- oral or injectable medications to make your body more sensitive to insulin
- changes to your diet, such as lower-carbohydrate, higher-fiber diet
- increased exercise
Less commonly, some people with type 2 diabetes become insulin-dependent.
Thyroid disease and diabetes
Thyroid disease and diabetes are related. According to the Diabetes Council, around 6.6 percent of the population has type 1 or type 2 diabetes. Diabetics of both types are more likely to have a thyroid condition. For example:
- If you have type 1 diabetes, you have a 33 percent chance of developing a thyroid condition. Because the risk of developing thyroid disease is so high for type 1 diabetics, the American Diabetes Association recommends that everyone diagnosed with type 1 diabetes have testing for thyroid disease, as well as regular follow-up testing.
- If you have type 2 diabetes, you have a 12 percent chance of having or developing a thyroid condition. The American Diabetes Association recommends that anyone diagnosed with type 2 diabetes also have thyroid testing at diagnosis, as well as regular follow-up testing.
The American Diabetes Council estimates that 10.8 percent of people with thyroid disease also have diabetes. The Diabetes Council also estimates that:
- 36 percent of people with hypothyroidism also has diabetes
- 12 percent of people with hyperthyroidism also has diabetes
- 11 percent of women with postpartum thyroiditis also has diabetes
If you have Hashimoto’s or Graves’ disease, you are more prone to developing type 1 diabetes.
And if you are hypothyroid from any cause — Hashimoto’s, radioactive iodine, or thyroid surgery — you are more prone to type 2 diabetes. Hypothyroidism is associated with insulin resistance, a key risk factor for type 2 diabetes. Even borderline hypothyroidism or undermedicated hypothyroidism increases your risk of progressing from insulin resistance/prediabetes to full type 2 diabetes.
Studies have also shown that for people with hypothyroidism, having a higher TSH level — even if you are being treated and your TSH falls within the reference range — puts you at a greater risk of developing type 2 diabetes.
Thyroid status and insulin treatment
If you are treating diabetes with insulin, thyroid disease can make it more difficult to manage your blood sugar levels.
Hyperthyroidism increases your metabolism and makes you metabolize medications more quickly. This includes insulin. If you are insulin-dependent, you may need a higher dose of insulin while hyperthyroid or overmedicated on thyroid hormone replacement medication. Otherwise, you are at risk of high blood sugar, known as hyperglycemia.
Hypothyroidism slows your metabolism and can slow the speed at which you metabolize medications. This includes insulin. If you are insulin-dependent, you may need lower doses, or you risk having low blood sugar, known as hypoglycemia.
Preventing type 2 diabetes
There are no proven ways to prevent type 1 diabetes. Type 2 diabetes, however, is preventable if you make changes that help you lower your blood sugar and increase your sensitivity to insulin. Some of the ways to accomplish these goals include the following:
- Optimal thyroid treatment. This means careful control of hypothyroidism or hyperthyroidism. Optimal hypothyroidism control usually means a TSH level less than 2.5, and free T4 and free T3 levels in the upper half of the reference range.
- Weight loss if you are overweight.
- Adding fiber to your diet, ideally consuming 25 to 30 grams of fiber daily.
- A low-carbohydrate, low-glycemic (low-sugar) or carbohydrate-controlled diet. Some diet approaches that have been effective at lowering blood sugar include the Paleo Diet, the Rosedale Diet, and intermittent fasting.
- Getting 7 to 8 hours of sleep nightly.
- Getting sufficient exercise — 10,000 steps or a minimum 30 minutes of moderate exercise daily.
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Mary Shomon is a thyroid disease, hormonal and autoimmune health writer, and patient advocate. For two decades, Mary has been a leading force advocating for more effective, patient-centered thyroid and hormonal health care. Mary is the New York Times bestselling author of “The Thyroid Diet Revolution,” “Your Healthy Pregnancy with Thyroid Disease,” “Living Well With Hypothyroidism,” and 10 other books on thyroid disease and integrative health. She co-stars in two PBS health specials, “Healthy Hormones,” and “Vibrant for Life.” Follow her on Twitter at @thyroidmary or at her Facebook communities: ThyroidSupport and ThyroidDiet.