Hypothyroidism and Diabetes

Learn about the symptoms, diagnosis, and treatment of this autoimmune disorder.


People with type 1 and type 2 diabetes have a high risk for hypothyroidism, a disorder that occurs when the thyroid gland produces lower amounts of thyroid hormones than the body needs.

This is important because hypothyroidism, which slows down the metabolism, can complicate blood sugar control. A slow metabolism (the rate that the body uses energy) means that diabetes medications can remain in the body longer, increasing the risk of hypoglycemia, or low blood sugars.

Hypothyroidism also increases total cholesterol and LDL (low-density lipoprotein or “bad cholesterol”) levels and causes increased triglyceride levels, all associated with heart disease and stroke.

People with type 1 diabetes, an autoimmune disorder, are particularly vulnerable to thyroid disorders. This is because people with one autoimmune disorder – a condition where the body attacks its own tissues and organs – are at a greater risk of developing additional autoimmune conditions like thyroid disease.

People with type 2 diabetes are also prone to develop thyroid disorders. Although the science is not yet clear, there may be a connection with aging, since type 2 diabetes and hypothyroidism often occurs in older adults. There may also be a connection with weight gain, since hypothyroidism is associated with additional weight.

What is Hypothyroidism?
The source of the problem is the thyroid, a butterfly-shaped gland located in the front of the neck below the larynx or voice box. Made up of two lobes, one located on either side of the windpipe, the job of the gland is to store hormones and release them into the bloodstream, where they circulate throughout the body, acting on virtually every tissue and cell.

The thyroid makes two hormones – triiodothyronine (T3) and thyroxine (T4). T3 is made from T4 and is the more active hormone, directly affecting the tissues.  If the thyroid releases too little of these hormones, it slows down the body’s metabolism (hypothyroidism).

Control of thyroid hormone production is regulated by thyroid stimulating hormone (TSH), which is made by the pituitary gland in the brain. When thyroid hormone levels are low, the pituitary releases more TSH; when they rise, it reduces production. One way to measure the health of the thyroid is a blood test to measure TSH.

The most common cause of hypothyroidism in the United States is  Hashimoto’s disease, where the immune system – designed to ward off bacteria and viruses – mistakenly attacks the thyroid gland.

What Are the Symptoms?
At first, it may be hard to tell the symptoms of a thyroid disorder. In some cases, there may be signs of a goiter, a swelling at the front of the throat, which signals an enlarged thyroid.

Hypothyroidism causes a number of uncomfortable signs and symptoms related to a slow down of the metabolism. These can include fatigue, weight gain, an intolerance to cold, joint and muscle pain, slowed heart rate, decreased sweating, heavy or irregular menstrual periods and impaired fertility, depression, and a slowed heart rate.

For people with type 2 diabetes, some of these symptoms may be easy to mistake for the diabetes itself.

How is Hypothyroidism Diagnosed and Treated?
Diagnosis of hypothyroidism is based on individual signs, symptoms, and tests.

Since symptoms do not always paint a clear picture of the disorder, if you have diabetes, particularly type 1, it’s important to have your thyroid checked regularly by lab tests. Ask your doctor what testing frequency is right for you. Typically, these tests are completed annually.

The most commonly used and most accurate screening test measures TSH levels. If your thyroid function is low, the TSH levels will be high since TSH stimulates additional production of thyroid hormones. Sometimes this test will measure a case of hypothyroidism that is subclinical, or borderline, but that still may be treated with medications.

Additional tests may be administered to help determine the diagnosis or confirm the cause of the hypothyroidism.

These include the T4 test, which looks at the actual amount of circulating thyroid hormone in the bloodstream. In hypothyroidism, the level will be lower than normal. If there is a suspicion of Hashimoto’s disease, the doctor may run a thyroid antibody test that searches for the presence of thyroid antibodies. Most people with Hashimoto’s disease have these antibodies, while people whose hypothyroidism is caused by other conditions do not.

Treatment for hypothyroidism involves taking a daily synthetic replacement hormone that is identical to T4 called levothyroxine (Levoxyl, Synthroid, and others). The TSH test is used to determine if the medicine is working and if it is being given in the correct dosage.

Updated on: January 24, 2019
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