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The Connection Between Thyroid Disease and Diabetes

Learn how diabetes and thyroid disease are two closely associated disorders in this article.
The Connection Between Thyroid Disease and Diabetes
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Thyroid disease and diabetes are the two most common endocrine disorders, and it's common for patients to have both conditions. Specifically, hypothyroidism, hyperthyroidism, or autoimmune thyroid disease all increase your risk of various forms of diabetes. Similarly, having any type of diabetes puts you at a higher risk of being diagnosed with a thyroid condition. Let's look at the connection, how both conditions can affect each other, and what hypothyroid patients need to know. 

Thyroid disease, insulin, and blood sugar

There's a clear connection between your thyroid hormones, insulin, and blood sugar (or glucose). The job of insulin – produced by your pancreas – is to help your cells take up glucose for energy. Because hyperthyroidism speeds up your metabolism, your body uses insulin more quickly than usual, leading to elevated blood sugar, known as hyperglycemia.

With hypothyroidism, your metabolism is typically slower, slowing down the rate you use insulin. This can lead to low blood sugar, known as hypoglycemia.

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Thyroid disease, prediabetes, and insulin resistance

Both hyperthyroidism and hypothyroidism are also associated with hyperglycemia and an increased risk of insulin resistance. According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), insulin resistance is "when cells in your muscles, fat, and liver don't respond well to insulin and can't easily take up glucose from your blood. As a result, your pancreas makes more insulin to help glucose enter your cells."

Over time, insulin resistance can develop into prediabetes. Your blood glucose levels are higher than average with prediabetes but not high enough to be officially diagnosed with diabetes. 

Prediabetes usually occurs in people who already have some level of insulin resistance or whose pancreatic beta cells aren't producing enough insulin to maintain normal blood glucose levels. Without enough insulin, you end with hyperglycemia, and extra glucose stays in your bloodstream.

People with prediabetes have up to a 50 percent chance of developing diabetes 5 to 10 years after diagnosis. 

The different types of diabetes

Type 1 diabetes

Type 1 diabetes, also called juvenile diabetes or insulin-dependent diabetes is a chronic autoimmune disease. In patients with Type 1 diabetes, the immune system attacks and destroys beta cells in the pancreas. These beta cells produce insulin, and once they are destroyed, the pancreas produces little or no insulin. The treatment for Type 1 diabetes is insulin.


Type 1.5 / Latent autoimmune diabetes in adults (LADA)

Type 1.5 / Latent Autoimmune Diabetes in Adults (LADA) is a form of autoimmune diabetes where antibodies attack the pancreas and make it unable to produce insulin. The onset of Type 1.5/LADA typically occurs after age 30. It can also be preceded by a period of insulin resistance, with some characteristics of Type 2 diabetes. Over time, in most cases, people with Type 1.5/LADA require insulin treatment due to low insulin levels. Type 1.5/LADA diabetes is a risk for patients with other autoimmune thyroid diseases. 


Type 2 diabetes

With Type 2 diabetes, there are two interrelated conditions: your pancreas is still capable of producing insulin – but not enough – and your cells are not responding well to insulin and, as a result, are less capable of taking in glucose. The treatment for type 2 diabetes is losing weight, eating well, exercising, and in many cases, medications that make you more sensitive to insulin. In some type 2 diabetes cases, insulin treatment is necessary.


Diagnosing prediabetes and diabetes

The three key tests to evaluate blood sugar as part of a diabetes diagnosis are:

  • Fasting Plasma Glucose (FPG), a measure of the fasting blood sugar level at the time of the test
  • Hemoglobin A1C (HA1C) shows your average blood glucose level over the past three months
  • Oral Glucose Tolerance (OGT) Test involves having a fasting glucose test, followed by drinking a glucose drink, and a second blood glucose measurement is taken 2 hours later

The following chart shows how these test levels are interpreted. 

In addition to blood sugar tests, a diagnosis of Type 1 diabetes is confirmed by positive one or more positive antibody tests, including: 

  • Islet cell antibodies (ICA)
  • Glutamic acid decarboxylase (GAD-65) antibodies (also known as GADA)
  • Insulin autoantibodies (IAA)
  • IA-2A

Diagnosis of Type 1.5/LADA diabetes is typically confirmed with:

  • Positive glutamic acid decarboxylase (GAD-65, or GADA) antibodies test
  • Low C-Peptide level of < 80 pmol/L


If you have thyroid disease, should you be screened for diabetes


Given the prevalence of undiagnosed and untreated insulin resistance, prediabetes, and diabetes in the general population – and the increased risk of diabetes in patients with hypothyroidism and autoimmune thyroid disease (like Hashimoto's disease) – regular screening of your thyroid hormone levels should be part of your overall wellness plan. At a minimum, if you're a hypothyroid patient, check with your doctor about including a Fasting Plasma Glucose and Hemoglobin A1C test as part of your annual checkups.


If you have prediabetes or diabetes, should you be screened for thyroid disease?

If you have prediabetes or are a diabetic patient, you should periodically get screened for thyroid disease. 

According to the Joslin Diabetes Center, around one-third of type 1 diabetic patients have markers for another autoimmune disease, frequently thyroid disease. It's imperative that thyroid testing for these diabetic patients includes thyroid antibodies tests. 

A clinical study has found that type 2 diabetic patients are also at significantly higher risk of thyroid conditions. 

If you have autoimmune type 1, type1.5/LADA diabetes, or type 2 diabetes, your wellness plan should periodically include a complete thyroid panel.

Getting a thyroid diagnosis

Diagnosing hypothyroidism in patients with diabetes starts with an examination of your thyroid gland and blood testing. You'll want to ask for or order a comprehensive panel of thyroid tests to include:

  • Thyroid Stimulating Hormone (TSH)
  • Free Thyroxine (Free T4)
  • Free Triiodothyronine (Free T3), and
  • Thyroid Peroxidase (TPO) antibodies


Your healthcare provider will evaluate your thyroid test results to make a diagnosis. Elevated TSH, low or low-normal Free T4, and low or low-normal Free T3 – along with a detailed medical history and symptoms assessment – can help confirm a diagnosis of hypothyroidism (an underactive thyroid gland).


If you have borderline or mild hypothyroidism, you may be diagnosed with subclinical hypothyroidism. Subclinical hypothyroidism is when peripheral thyroid hormone levels (T3 & T4) are within the normal reference range, but thyroid-stimulating hormone (TSH) levels are mildly elevated.


Thyroid medications for treatment

The treatment for hypothyroidism is thyroid hormone replacement medication. Hypothyroid patients are treated with drugs, including the synthetic T4 therapy known as levothyroxine (Synthroid, Levoxyl, Euthyrox, and Thyrolar), the synthetic T3 drug liothyronine (Cytomel), and natural desiccated thyroid (NDT) drugs like Armour and NP Thyroid. In some cases, thyroid medications are custom-compounded to more precisely treat hypothyroidism.


An important note for thyroid patients with diabetes

Hypothyroid patients should make sure that treatment decisions and diagnoses aren't solely based on their HA1C results. Research suggests that when untreated, hypothyroidism can artificially increase HA1C test results. At the same time, thyroid treatment can falsely lower HA1C results. Meanwhile, fasting blood sugar levels may remain unchanged. Therefore, treatment decisions for people with diabetes in thyroid patients should always include the fasting blood sugar results to avoid the risk of undertreatment, overtreatment, or misdiagnosis.


A note From Paloma Health

Periodic thyroid screening and monitoring is a health care essential. The Paloma Complete Thyroid Blood Test kit can make thyroid testing – and regular thyroid screening -- easy and affordable right from home. Your at-home thyroid test kit comes with everything you need for sample collection and sample analysis of TSH, free T3, free T4, and TPO antibodies, with the option to add on reverse T3 and/or vitamin D.

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Your thyroid test kit is sent directly to your address, requires an easy finger prick, and then sent back to the lab with pre-paid shipping. Your thyroid lab results are released to your secure online dashboard within days, similar to the wait time for in-person lab results, without the inconvenience. 

Suppose your lab results indicate an underactive thyroid. In that case, you can schedule a virtual visit with one of our top thyroid doctors. Paloma Health's doctors partner with you to determine the best treatment plan and thyroid medication to safely normalize your thyroid function and resolve your thyroid symptoms if you require hypothyroidism treatment.

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Mary Shomon

Patient Advocate

Mary Shomon is an internationally-recognized writer, award-winning patient advocate, health coach, and activist, and the New York Times bestselling author of 15 books on health and wellness, including the Thyroid Diet Revolution and Living Well With Hypothyroidism. On social media, Mary empowers and informs a community of more than a quarter million patients who have thyroid and hormonal health challenges.

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