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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Both diabetes and thyroid disorders are known 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, can lead to a wide range of symptoms.

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

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

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 hypo- and hyperthyroidism, respectively.

The pancreas is a gland in the abdomen that plays a role in the digestive system. It also produces insulin, a hormone that is responsible for allowing glucose in the blood to enter cells, providing them with the energy to function. Without enough or effective 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.

In someone with hyperthyroidism, blood sugar levels may spike rapidly after the person eats. Thyroid hormone stimulates the release of glucagon in the pancreas. Glucagon is a type of stored sugar, and the body releases it when blood sugar levels are too low, a condition known as hypoglycemia. The body stops releasing it when blood sugar levels return to a healthy range.

An overactive thyroid will release glucagon even when it is not necessary. This release of extra sugar can increase a person’s blood sugar levels. An excess of glucagon is a key factor in the development of diabetes.

Evidence suggests that there is a link between both hyper- and hypothyroidism and insulin resistance. 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 as a result of hyperthyroidism because of an increase in fatty free acids in the bloodstream. In body fat, 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 acids can hinder insulin secretion and cause insulin resistance.

A 2017 review found that even small increases in thyroid stimulating hormone (TSH), which tends to be high in hypothyroidism, can be linked to insulin resistance. Research suggests that hypothyroidism may cause insulin resistance partially because it limits how much insulin can increase glucose utilization in the muscle.

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

Some forms of thyroid disorder are autoimmune diseases. Research suggests that the autoimmune response that causes type 1 diabetes is closely associated with 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.

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

Cortisol can increase blood sugar levels. Too much cortisol can lead to hyperglycemia and decreased thyroid hormone levels, while too little can lead to hypoglycemia and higher thyroid hormone levels. Cortisol can also increase insulin resistance. 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, managing blood pressure and cholesterol, and trying to stop smoking if they do
  • 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 hyperthyroidism, including:

  • antithyroid drugs
  • radioactive iodine
  • beta-blockers
  • surgery

Additionally, it may be advisable to screen individuals who currently live with one of these conditions for the other. For example, some evidence suggests it may be beneficial to screen people living with type 1 and type 2 diabetes for a thyroid disorder.

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

Common symptoms of diabetes include frequent urination, fatigue, and increased thirst and hunger. Symptoms of hypothyroidism can include feeling cold and tired and having dry skin. For hyperthyroidism, symptoms may include irritability, sweating, and 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 that they might also have the other condition. The authors of a 2020 study on the relationship between diabetes and thyroid dysfunction suggest that people with all types 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. If a person is concerned about either condition, they should contact a doctor.