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Diabetes and Your Thyroid: What’s the Connection?

Last updated: May 2022

If you live with type 2 diabetes, there's a chance you also live with another health condition: thyroid disease. There are many different risk factors for thyroid disease, including diabetes. 

Poorly managed type 2 diabetes can increase the chance of thyroid issues, like your thyroid growing larger than normal or growing lumps on it. This is linked to higher insulin levels in your bloodstream and insulin resistance.1

What does your thyroid do?

The thyroid releases hormones into the bloodstream. These hormones impact how your body uses energy, including lipids (fats), glucose (sugar), and proteins. Thyroid hormones affect cells and organs across all of your body.2

How is thyroid disease diagnosed?

Your primary care provider (PCP) can check your thyroid health by testing your blood. Another method of diagnosing thyroid health is through a physical exam. Your doctor may touch the front of your neck to check for abnormal lumps or bumps on your thyroid.

However, if your lab work or physical exam shows signs of thyroid issues, other tests can be used to take a closer look. These tests include ultrasounds, thyroid scans, and the radioactive iodine uptake test. Common thyroid labs include TSH, T4, and T3.3

What is TSH?

TSH is a hormone from the pituitary gland that tells your thyroid how much T3 and T4 to make. A high TSH is often connected with hypothyroidism. Low TSH is associated with hyperthyroidism. If your TSH levels are too high or low, your doctor will likely check your T4 and T3.

T4 levels

A high level of T4 in your lab results can signal that you have hyperthyroidism. A low T4 level may mean you have hypothyroidism.

T3 levels

Your T3 levels can give your doctor more insight to diagnose a thyroid issue if the other labs provide supportive information.

What is hyperthyroidism?

Hyperthyroidism is when your body has more thyroid hormones than it needs. Hyperthyroidism causes your body to speed up certain bodily functions.

For example, your digestion can be faster than normal (you go to the bathroom more often), your heart rate is faster than normal, or your metabolism can be faster (you may start losing weight).

Impact on people with type 2 diabetes

Hyperthyroidism can cause higher blood sugars in those with type 2 diabetes, increasing the risk of diabetes complications.1,2

What is hypothyroidism?

Hypothyroidism is when your body has fewer thyroid hormones than it needs. This causes your body to slow down its work. Weight gain, depression, slower digestion (constipation), and tiredness are some things that come along with a hypothyroid diagnosis.

Subclinical hypothyroidism and diabetes

Hypothyroidism can be missed in the early stages or if it's mild enough that it doesn't cause symptoms (this is called subclinical hypothyroidism). 

However, subclinical hypothyroidism can still cause high blood pressure and high cholesterol, which need to be well-managed in diabetes. It also lowers your body's ability to release insulin when needed and affects the small and large blood vessels, increasing your risk of diabetes complications.1,4

Monitor your thyroid health

The connections between your thyroid and diabetes and how they impact each other and your overall health make thyroid health important. Ask your PCP or endocrinologist if thyroid testing is right for you and how often you may need it.

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