Diabetes and thyroid disorders are relatively common conditions that involve problems with hormones. While researchers are unsure of the exact cause, growing evidence suggests a link between these conditions.

Thyroid disorders and diabetes are two of the most common conditions that endocrinologists treat. The term “endocrine disorder” describes a group of conditions that affect the production and release of hormones. People living with one of these conditions may be at a higher risk of developing the other.

This article will discuss the relationship between diabetes and thyroid disorders.

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Experts refer to both diabetes and thyroid disorders as endocrine disorders. This term refers to medical conditions in which the endocrine system, which produces hormones, does not function correctly. These conditions can have several potential causes, and because they affect hormones, they can lead to a wide range of symptoms.

The endocrine system consists of eight major glands throughout the body, including the thyroid and pancreas.

The thyroid is a butterfly-shaped gland that sits at the front of the neck. It produces hormones, such as thyroxine (T4) and triiodothyronine (T3), which help regulate body processes — such as metabolism, mood, breathing, and heart rate.

In some cases, the thyroid may overproduce hormones, causing a condition known as hyperthyroidism, or underproduce hormones, a condition known as hypothyroidism.

Autoimmune conditions can often result in the development of these thyroid disorders. Hashimoto’s thyroiditis and Graves’ disease are common causes of hypothyroidism and hyperthyroidism, respectively.

The pancreas is a gland in the abdomen that plays a role in the digestive system. It produces insulin, a hormone that helps blood sugar, or glucose, enter cells, providing the cells and body with essential energy. Without enough insulin, a person may develop diabetes.

Diabetes is a group of conditions that affects the body’s ability to process blood glucose. There are multiple types of diabetes, with type 1 and type 2 being the most common.

In type 1 diabetes, the immune system mistakenly attacks the pancreas, reducing insulin production. In type 2, many variables, such as lifestyle factors, genes, and insulin resistance, may contribute to the development of the condition.

The thyroid secretes hormones that regulate a person’s metabolism. An imbalance in these hormones can affect a person’s blood sugar in several ways.

Excess thyroid hormone increases lipolysis and secretion of both insulin and glucagon, and the sum of these effects deteriorates glucose metabolism, which can cause glucose intolerance and diabetes.

Glucagon is a hormone that the pancreas releases when a person experiences hypoglycemia, a condition in which their blood sugar levels are too low. The body stops releasing glucagon when the blood sugar levels return to a healthy range.

According to a 2016 review, an excess of glucagon is the key factor in the development of diabetes.

Evidence suggests that there is a link between insulin resistance and both hyperthyroidism and hypothyroidism. Because thyroid hormones are essential for carbohydrate metabolism, thyroid dysfunction can impact insulin and lead to the development of type 2 diabetes.

Insulin resistance may occur due to hyperthyroidism because of an increase in fatty free acids in the bloodstream. In body fat, the thyroid hormone stimulates a process called lipolysis, which involves the breakdown of body fat into serum-free fatty acids.

Research suggests there is a link between the levels of serum-free fatty acids and diabetes because these fatty acids can hinder insulin secretion and cause insulin resistance.

A 2017 review found a link between insulin resistance and even small increases in the thyroid stimulating hormone (TSH), which tends to be high in hypothyroidism. Research suggests there is an association between hypothyroidism and insulin resistance partially because of insulin’s decreased ability to increase glucose utilization in muscle.

Because hypothyroidism can slow metabolism, insulin stays in the bloodstream longer. This suggests that a person with diabetes and hypothyroidism may require a lower dose of insulin for their treatment.

Some forms of thyroid disorders are autoimmune diseases. Research suggests that there is a close association between the autoimmune response that causes type 1 diabetes and autoimmune-induced thyroid dysfunction (AITD).

An estimated 17–30% of adults with type 1 diabetes also have AITD. Additionally, 25% of children with type 1 diabetes have autoimmune hypothyroidism. Research suggests that genetic factors may contribute to this.

The hypothalamic-pituitary-adrenal (HPA) axis, or the interaction of the hypothalamus, pituitary gland, and adrenal glands, may be another possible link between diabetes and the thyroid. These glands secrete hormones into the blood and help manage reactions to stress by regulating levels of the hormone cortisol.

Too much cortisol can increase a person’s glucose levels by stimulating the liver to increase new glucose formation, causing a state of insulin resistance and a decrease in insulin secretion.

As such, problems with the HPA axis can lead to abnormal blood sugar levels and affect the body’s response to insulin.

In many cases, it may not be possible to prevent diabetes or thyroid disorders. At present, there is no guaranteed way to prevent an autoimmune disease from developing. However, a person may be able to prevent or delay the onset of conditions that do not have genetic causes.

For example, it is possible to prevent type 2 diabetes by eating a nutritious diet, exercising regularly, and maintaining a healthy weight.

To help manage diabetes, a person can create a diabetes self-care plan, which may include:

  • achieving A1C targets and managing blood pressure and cholesterol
  • not smoking or quitting if a person does smoke
  • following a meal plan
  • getting regular exercise
  • taking medication, such as insulin
  • checking blood glucose levels regularly
  • working closely with a diabetes healthcare team

The treatment for thyroid disorders will depend on whether the thyroid gland is under- or overactive. While there is currently no cure for hypothyroidism, a person can manage it with medication. By taking T4 replacements, a person can increase their T4 and return their TSH to a healthy level.

Some treatment options are available to help a person manage their hyperthyroidism, including:

Additionally, a doctor may advise screening individuals currently living with one of these conditions for the other condition. For example, some evidence suggests it may be beneficial to screen people living with type 1 or type 2 diabetes for a thyroid disorder.

Anyone who suspects they might have diabetes or a thyroid dysfunction should contact a doctor.

Common symptoms of diabetes include frequent urination, fatigue, and increased thirst and hunger. Symptoms of hypothyroidism can include having dry skin and feeling cold and tired. For hyperthyroidism, symptoms may include irritability, sweating, and a thinning of the skin.

A person should also contact a doctor if they are already living with either diabetes or a thyroid disorder and suspect they might also have the other condition.

Data from a 2020 study on the relationship between diabetes and thyroid dysfunction suggest that people with any type of diabetes should routinely test for thyroid dysfunction.

Evidence suggests close links between thyroid disorders and diabetes. Thyroid dysfunction can affect a person’s insulin and blood sugar levels, which can contribute to the development of diabetes.

Both under- and overactive thyroids are more common in people with diabetes than in the general population. A person concerned about either condition should contact a doctor.