Hyperthyroidism and Diabetes

Written by Ilene Raymond Rush
Reviewed by Amy Hess-Fischl, MS, RD, LDN, BC-ADM, CDE

People with type 1 diabetes are at a high risk for hyperthyroidism, a condition caused by the overproduction of thyroid hormones. This excess of hormones speeds up the metabolism, the rate at which the body uses energy.

Hyperthyroidism is usually associated with poor blood glucose control and a need for additional insulin.  A increased metabolism “clears” insulin from the system at a faster rate, and an increased production and absorption of glucose can raise blood sugars.

All of this can lead to insulin resistance – where cells are unable to respond to insulin in order to use glucose for energy. In extreme cases, this can lead to dangerously high blood sugars and diabetic ketoacidosis.

Hyperthyroidism can also aggravate diabetic heart conditions. It can cause a rapid heart rate as well as arrhythmia (an irregular heartbeat).

People with type 1 diabetes are particularly vulnerable to developing hyperthyroidism because thyroid disorders often result from problems with the immune system. The most common cause of hyperthyroidism in people under 40 is Graves’ disease, an autoimmune disorder.

People with type 2 diabetes can also be affected by hyperthyroidism. However, people with type 2 are more likely to have hypothyroidism, a condition where the body produces too little thyroid hormones and the metabolism is slowed.


What is Hyperthyroidism?
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. The thyroid consists 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 much of these hormones, it speeds up the body’s metabolism (hyperthyroidism).

Control of thyroid hormone production is regulated by thyroid stimulating hormone (TSH). TSH 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.  By measuring TSH in the bloodstream, your doctor can assess the health of your thyroid.

In Graves’ disease, the immune system makes an antibody called thyroid- stimulating immunoglobulin (TSI) that attaches to thyroid cells.  TSI mimics the action of TSH and stimulates the thyroid to make excessive thyroid hormones.

What Are the Symptoms?
Symptoms of hyperthyroidism include nervousness or irritability; fatigue or muscle weakness; trouble sleeping; hand tremors; rapid or irregular heartbeat; frequent bowel movements; weight loss; mood swings; and a goiter, an enlarged thyroid that causes the neck to appear swollen.

In older women, some of these symptoms may be confused with menopause. In younger patients, they may be mistaken for signs of poorly-controlled diabetes.

How is Hyperthyroidism Diagnosed and Treated?
Because these symptoms may be mistaken for other conditions, if you are experiencing them, it’s important to get tested by your physician. Even if you aren’t experiencing symptoms, if you have diabetes you should talk to your doctor about your need for thyroid screening.

The most commonly administered test measures the thyroid-stimulating hormone (TSH). TSH regulates the production of thyroid hormones, so in the case of an overactive thyroid, the level of TSH will be low, since the hormone will be trying to put the brakes on hormone production.

Additional tests may also be recommended, including a thyroid-stimulating immunoglobulin (TSI) test to measure the amount of TSI in the blood. Most people with Graves’ disease will have this antibody.

Measuring the amount of iodine the thyroid collects from the bloodstream can also help diagnose the problem. High levels of iodine could indicate Graves’ disease. In some cases a thyroid scan may also help uncover the cause of hyperthyroidism.

Several treatments are available for hyperthyroidism. In cases of Graves’ disease, radioactive iodine therapy is the most common therapy used in the United States. Surgery is another alternative, particularly to address large goiters. Long-term oral antithyroid medications, such as methimazole (Tapazole) and propopylthiouracil (PTU), can control the production of the thyroid hormone.

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