Hyperthyroidism and diabetes are both diseases that result from endocrine dysfunction. It is common, particularly in adolescence and childhood, for children diagnosed with type 1 diabetes to also be diagnosed with thyroid disease.
Hyperthyroidism and diabetes are closely linked. Increased levels of thyroid hormone change how the body produces insulin and reacts to it, as well as other short- and long-term changes affecting blood-glucose levels. These effects increase the risk of diabetes, although overt (clear) diabetes in those with hyperthyroidism is still rare.
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Your thyroid gland is a vital hormone-producing gland that plays a significant role in the human body's growth, development, and functions. It is located at the base of the throat and is responsible for releasing thyroid hormones into your bloodstream.
Thyroid hormones play a vital role in regulating your body's metabolism. Metabolism is the process that converts the food you eat into energy and supports the bodily processes necessary for living. This energy is then used throughout your body to keep its systems functioning properly.
The thyroid gland produces two hormones in the follicular epithelial cells:
Triiodothyronine, or T3 (also produced in many other tissues)
Tetraiodothyronine, also known as thyroxine or T4
When your thyroid functions correctly, it produces the right amount of thyroid hormones needed to keep your metabolism operating at the optimal rate.
The pituitary gland governs the thyroid gland and the production of thyroid hormones. Located at the base of your brain, your pituitary gland monitors thyroid hormone levels in your bloodstream and produces a hormone called thyroid-stimulating hormone (TSH). When the pituitary gland senses high or low levels of thyroid hormones, it adjusts the amount of TSH it produces, which signals the thyroid gland to release more or fewer hormones into the bloodstream to get the body back to normal.
Source: Regulation of Thyroid Function, Synthesis and Function of Thyroid Hormones¹
Hyperthyroidism, or overactive thyroid, occurs when your thyroid gland produces more thyroid hormones than your body needs. It can also happen if you take an excessive amount of thyroid hormones.
When you have high levels of thyroid hormones in your bloodstream, your metabolism increases, which in turn escalates many bodily functions. Hyperthyroidism can affect your heart rate, breathing, digestion, weight, and mood and, if not treated, can lead to serious medical issues.
When your thyroid produces too many hormones, it can speed up every body's function. Symptoms of hyperthyroidism often include:
More frequent bowel movements
Weight loss despite an increased appetite and eating well
In addition, symptoms of hyperthyroidism may include:
Thinning of your skin
Hair loss and changes in hair texture that make it brittle
Weakness in your muscles
Hyperthyroidism increases metabolism, causing many individuals to feel hyperactive, nervous, or anxious due to having too much energy. The most common cause of hyperthyroidism is an autoimmune disorder called ‘Graves' disease’. This illness may cause the eyes to bulge and appear enlarged, and some patients also have swelling in the neck from an enlarged thyroid gland.
Several studies have found an increased prevalence of thyroid disorders in patients with diabetes and vice versa. In addition, research shows that hyperthyroidism is closely linked with hyperglycemia² (high blood sugar).
Thyroid disease is characterized by a change in thyroid hormone levels that affects your metabolism. The changes in your metabolism can cause glucose that the body would usually use to become excessive.
You are also at a greater risk of developing a condition known as ‘metabolic syndrome’ if you:
Have a family history of metabolic syndrome
Are physically inactive
Have insulin resistance
Metabolic syndrome is a cluster of abnormalities marked by hypertension, abnormal glucose levels or insulin resistance, and dyslipidemia, a condition characterized by abnormally elevated cholesterol or fats in the blood. Metabolic syndrome increases your risk of heart disease, nonalcoholic fatty liver disease, and type 2 diabetes.
Production of insulin
Thyroid disease also interferes with the production of insulin, which enables the cells in your body to use glucose for energy, and helps to control blood sugar levels. Several studies have shown that increased thyroid hormone levels speed up the elimination of insulin³, thus putting patients at further risk of higher than normal blood sugar levels and even type 2 diabetes or prediabetes.
Hyperthyroidism and diabetes are also connected by a group of organs that influence the production of thyroid hormones and insulin. The hypothalamus, pituitary gland, and thyroid glands, commonly referred to as the ‘HPT axis’, work together to determine the set point of thyroid hormone production.
The hypothalamus releases a hormone that stimulates the synthesis and release of thyroid-stimulating hormone from the pituitary gland, which causes the thyroid to produce and release thyroid hormones.
The hypothalamus and the pituitary gland also work hand in hand with the adrenal glands via the so-called ‘HPA axis,’ managing the levels of the ‘stress hormone’, cortisol. Any problem with one of the organs in the HPA axis can affect the amount of cortisol produced.
High cortisol levels⁴ caused by issues with the HPA axis are associated with hyperglycemia and decreased thyroid hormone levels.
Type 1 diabetes is an autoimmune disorder. Autoimmune disorders are conditions where a person’s immune system attacks their own body. In the case of type 1 diabetes, the immune system attacks the cells responsible for producing insulin.
Studies have discovered that people with one type of autoimmune disorder are often at risk of developing another. For example, patients with type 1 diabetes have an increased risk of developing an autoimmune thyroid disease⁵ such as Hashimoto's thyroiditis or Graves' disease.
Graves' disease is a common cause of hyperthyroidism and is frequently associated with type 1 diabetes⁶. Many studies have confirmed the frequent occurrence of autoimmune diseases in diabetic patients⁷, with over 17% of patients diagnosed with Hashimoto's disease also being diagnosed with type 1 diabetes.
Globalization does more than just spread goods, knowledge, and experience that helps a nation's economy. For example, as the world becomes smaller and more of our cultures are shared, there is also an increase in the spread of chronic health problems⁸, such as diabetes.
Once a condition primarily affecting people in wealthy countries, diabetes is now a global epidemic affecting 285 million to 347 million people and accounting for nearly 10% of all global spending on adults.
A large European meta-analysis⁹ discovered that thyroid disease is found in about 3.82% of the general population.
However, thyroid disease is considerably more common in people with type 2 diabetes¹⁰, ranging from 9.9% to 48%. This wide range of prevalence is due to different definitions for thyroid disease diagnosis.
There are many risk factors associated with hyperthyroidism in the general population. The risk factors for thyroid disease among people with diabetes¹¹ are similar to many of these.
Like in nondiabetics, an enlarged thyroid gland, known as a ‘goiter’, is recognized as a risk factor for thyroid disease in diabetic patients. The duration of the diabetic condition has also been found to increase the risk of developing thyroid autoimmune diseases in children and adolescents with type 1 diabetes.
Your risks are also higher if you:
Eat large amounts of food containing iodine
Were pregnant within the past six months (postpartum thyroiditis)
The American Thyroid Association (ATA) recommends that adults be screened for thyroid disorders at age 35 and every five years after that¹². The ATA suggests screening by measuring the serum thyrotropin (TSH) concentration at regular intervals, whether the person has diabetes or not.
Children with type 1 diabetes should also be regularly screened for thyroid disorders.
While thyroid disease affects more women than men, screenings are a relatively cost-effective method of ensuring the health of your thyroid gland regardless of gender. In addition, your doctor may require more frequent serum thyrotropin testing if you have signs or symptoms potentially caused by a thyroid disorder or have other risk factors for its development.
Research shows that thyroid disorders and diabetes mutually influence each other, and the association between the two conditions has long been recognized. Both diabetes and thyroid disorders involve a dysfunction of the endocrine system, and thyroid hormones greatly influence the metabolism, which can significantly impact the control of blood sugar levels.
Studies have shown that diabetes and thyroid disorders tend to coexist in patients. With the close relationship between the two conditions, you should also get tested for diabetes if you have an overactive thyroid.
While hyperthyroidism cannot be prevented with lifestyle changes, alterations to certain factors in your way of life play a crucial role in preventing and controlling diabetes. You can reduce your risk by making healthy changes to your lifestyle and diet:
Avoid alcohol and tobacco products
Avoid refined foods, such as white bread, pasta, and sugar
Reduce or eliminate trans fatty acids commonly found in commercially manufactured foods like cookies, crackers, cakes, and margarine
Limit the amount of processed foods you eat, such as fast food or lunch meats, and eat less red meat.
Use healthy cooking oils like olive or coconut oil
Eat more lean meats or get your protein from cold-water fish or beans
If possible, get physically active and exercise for 30 minutes daily, five days a week.
Lifestyle changes, including losing weight, eating healthily, and engaging in regular, moderate physical activity, can help control Type 1 diabetes and slow the progression of prediabetes and Type 2 diabetes¹³. These steps also reduce other risk factors such as high blood pressure, blood cholesterol, heart attacks, and strokes.
In many cases, people with diabetes may require medication to control blood sugar levels along with lifestyle changes. At the same time, people with hyperthyroidism¹⁴ will most likely require additional treatments to regulate thyroid hormone levels.
If you see a doctor for hyperthyroidism or diabetes, you should talk to them about being tested for the other condition.
You should also consult with your doctor if you are experiencing common symptoms of hyperthyroidism or diabetes.
Typical symptoms of hyperthyroidism include:
Shortness of breath
Signs and symptoms of diabetes include:
Unexplained weight loss despite a normal or increased appetite
Anxiety and irritability
If you're experiencing any of the above, it's vital to see your doctor so they can assess your condition and recommend treatment. If you're experiencing severe symptoms, you should seek emergency treatment immediately.
It's common for someone to have both thyroid disease and diabetes. Usually, if you have type 1 diabetes or type 2 diabetes, you have an increased risk of developing a thyroid disorder. Similarly, if you have a thyroid disorder, you are at an increased risk of developing metabolic syndrome or type 2 diabetes.
The relationship between hyperthyroidism and diabetes is fairly well documented. In addition, the frequency of patients developing hyperthyroidism and diabetes simultaneously is great enough that patients diagnosed with one of the conditions should be tested for the other.
Plasma adrenocorticotropin (ACTH) values and cortisol response to 250 and 1 μg ACTH stimulation in patients with hyperthyroidism before and after carbimazole therapy: Case-control comparative study (2007)
Preventing and treating diabetes | American Heart Association
Hyperthyroidism | Mount Sinai