Diabetes and an underactive thyroid
Thyroid conditions and diabetes are the two most frequent hormonal problems general practitioners encounter in their daily practice (1).
Today diabetes is grouped in two main forms: type 1 and type 2 diabetes. Both type 1 and 2 diabetes can occur in people diagnosed with Hashimoto’s and an underactive thyroid (1).
Thyroid function and diabetes
Thyroid hormones are necessary for the body to metabolize carbohydrates, as well as for the pancreas to properly function (the organ producing insulin). Low thyroid hormones cause a drop in insulin levels — insulin is a hormone needed to take sugar from the blood to different cells throughout the body.
Low insulin levels cause high blood sugar levels and slows down in cellular function, including muscle contractions and basic brain function. Over longer periods of time low insulin levels can trigger diabetes.
People are at an increased risk of frequent hypoglycemic episodes with an underactive thyroid and low blood sugar symptoms include:
- Problems talking
- A feeling of hunger
- Loss of consciousness (in extreme cases) (2–4).
Both clinical and subclinical hypothyroidism are connected to insulin resistance, a state where cells in the body stop responding to insulin’s signal to take sugar out of the blood. This results in high blood sugar levels, directly increasing the risk of eye damage and kidney damage (2–4). Insulin resistance can cause the thyroid gland to develop more nodules and become larger in size (5, 6).
Symptoms of insulin resistance include:
- Brain fog
- Weight gain (especially around the belly)
- High blood pressure
People who are diagnosed with diabetes, but are not managing it through lifestyle interventions, are at risk of having lower levels of T3 hormone and high rT3 levels (7,8).
Hashimoto’s and type 1 diabetes
Type 1 diabetes is the most common chronic hormonal condition in children and young people — 4 in 100 children with diabetes type 1 also have Hashimoto’s (9). 1 in 2 relatives of people with type 1 diabetes have an autoimmune thyroid condition (10 -12).
4 in 10 adult patients with type 1 diabetes test positive for TPO antibodies, and are at risk for developing an underactive thyroid (13–15). Type 1 diabetes patients who test positive for glutamic acid decarboxylase antibodies (GADA) have a three and half times higher risk of developing a thyroid condition (16).
3 in 10 adults diagnosed with Hashimoto’s have type 1 diabetes — only half of these patients will have an underactive thyroid, while the other half will have TSH within normal ranges (10, 17).
Type 1 diabetes and Hashimoto’s co-occur often and are inherited, as they share several genes, whose mutation increases the risk of developing either type 1 diabetes, Hashimoto’s, or both (18–25).
Type 1 diabetes patients at an increased risk of developing Hashimoto’s and an underactive thyroid include (17, 26–31):
- Older people
- Positive for glutamic acid decarboxylase antibodies (GADA)
- Have had type 1 diabetes for a long time
Hashimoto’s and type 2 diabetes
1 in 10 people with diabetes type 2 will have a thyroid condition too. Women with type 2 diabetes are five times more likely to have Hashimoto’s (32).
The American Thyroid Association guidelines for type 2 diabetes patients advises for frequent thyroid function testing (17).
Risk factors of having both type 2 diabetes and Hashimoto’s include:
- High TPO antibodies in thyroid patients
- High estrogen levels and polycystic ovary syndrome (PCOS)
- Overweight and obesity
Metformin — a medication used to treat patients with type 2 diabetes, obesity, and/or people with PCOS — can normalize TSH levels in diabetic patients with an underactive thyroid (33).
Diabetes is a broad condition with many genetic and environmental triggers, as well as many symptoms and co-occurring conditions. A year ago researchers have further classified diabetes in five instead of two groups, and some of them are more associated with autoimmune conditions (34).
How we write: our information is based on the results of peer reviewed studies using the National Library of Medicine platform. It is written by scientists and reviewed by external experts. If you believe we might have overseen crucial scientific information, please contact us at email@example.com
Disclaimer: This information is not intended to mitigate, prevent, treat, cure or diagnose any disease or condition. If you want to change your treatment, lifestyle, your diet, include supplements in your diet or have concerns about your health, please consult your doctor before trying new approaches.
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- Fleiner HF, et al. Prevalence of Thyroid Dysfunction in Autoimmune and Type 2 Diabetes: The Population-Based HUNT Study in Norway, 2016
- Cappelli C, et al. TSH-lowering effect of metformin in type 2 diabetic patients: differences between euthyroid, untreated hypothyroid, and euthyroid on L-T4 therapy patients, 2009
- Ahlquist E, et al. Novel subgroups of adult-onset diabetes and their association with outcomes: a data-driven cluster analysis of six variables, 2018
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