Thyroid Disease 101

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

An overactive thyroid (hyperthyroidism) can create problems with glucose control and insulin resistance, while an underactive thyroid (hypothyroidism) can boost your cholesterol. Both can exacerbate heart and stroke issues, already a problem for people with diabetes.

It is estimated that about 13 percent of people with diabetes have thyroid disease, with more women affected by the disorder.

Like type 1 diabetes, an autoimmune disease, the most common types of thyroid disorders are also autoimmune disorders, which are often inherited conditions. Autoimmune diseases occur when the immune system, designed to protect the body against bacteria and viruses, attacks the bodies’ own tissues. People who already have one autoimmune condition often have an increased chance of developing a second.

But people with type 2 diabetes, which is not an autoimmune condition, can develop thyroid problems as well.

Why is the Thyroid Important?
The source of the problem is the thyroid, a small 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 much of these hormones the metabolism rate — how the body employs energy — speeds up (hyperthyroidism) and if it releases too little it slows down (hypothyroidism). Often hyperthyroidism is found in type 1 and hypothyroidism in type 2, but that isn’t always the case.

Control of thyroid hormone production is regulated by thyroid stimulating hormone (TSH) 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.

Hypothyroidism and Hyperthyroidism
Hypothyroidism, or underactive thyroid, is the most common disorder of the thyroid. This slowing down of thyroid hormones can affect the workings of the entire body, including brain development, breathing, heart and nervous system functions, temperature, muscle strength, skin dryness, menstrual cycles, weight, and cholesterol levels.

For people with diabetes, hypothyroidism rarely causes significant changes in blood glucose control, although in some cases it can prevent insulin from being cleared in the bloodstream, so insulin dosages may need to be adjusted. Hypothyroidism can, however, create a number of abnormalities in blood lipid levels, including higher total cholesterol and LDL (low-density lipoprotein or ‘bad’ cholesterol levels), and increased levels of triglycerides.

Hyperthyroidism occurs when the thyroid gland pumps out more hormones than the body needs. Graves disease, an autoimmune disease, is the most common type of hyperthyroidism in the U.S. Like hypothyroidism, the disorder impacts the metabolism and organs throughout the entire body.

Hyperthyroidism puts the body in overdrive, which can create problems with blood glucose control.  Increased levels of thyroid hormones in the bloodstream can stimulate a increased production of glucose in the liver, cause a rapid absorption of glucose through the intestines and increase insulin resistance, a condition where the body does not utilize insulin effectively.

Screening Guidelines for Thyroid Disease
Guidelines from the American Diabetes Association suggest screening children with type 1 diabetes for antibodies for thyroid disease soon after diagnosis and to measure concentrations of TSH after metabolic control has been established. If normal, the guidelines suggest rechecking every one to two years. 

According to the American Thyroid Association type 2 patients should have their TSH levels checked at diagnosis or age thirty-five and then every five years. The American Association of Clinical Endocrinologists suggests palpitation of the thyroid at regular checkups to screen for a goiter caused by excessive pumping of hormones by the thyroid.

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Hypothyroidism and Diabetes