By Amy Adams, MS

Reviewed By Jeremy Walston, MD and Kristi Silver, MD
Last Updated: September 15, 2000

In Type 1 diabetes, the immune system attacks the pancreas cells that produce insulin. Without insulin, Type 1 diabetics are unable to use a sugar called glucose as fuel. When the immune system attacks cells of the body in this way, it is called an autoimmune disease. Diabetes is not the only autoimmune disease that family members of Type 1 diabetics are at risk for developing. In addition to diabetes, Type 1 diabetics and their families are at a higher risk than the general population for developing other autoimmune diseases, particularly thyroid disease.

Autoimmune Disease in Families

Type 1 diabetics and their family members have a 20 percent risk for developing autoimmune disease. The most common form of autoimmune disease in families with Type 1 diabetes is thyroid disease. In fact, 15 to 20 percent of diabetics and their siblings or parents have evidence of thyroid autoimmune disease compared to 4.5 percent in the general population. As in the general population, more female than male diabetics develop thyroid autoimmunity.

An autoimmune reaction against cells of the intestine (parietal cells) is also common in Type 1 diabetics and their families. Antibodies against the parietal cells are found in five to twelve percent of Type 1 diabetics and in two to six percent of their parents or siblings.

Families with a Type 1 diabetic are at risk for the following autoimmune diseases:

• Thyroid (Graves disease, Hashimoto's thyroiditis). Autoimmune disease against the thyroid can cause either increased or decreased thyroid function. Because the thyroid is involved in metabolism, thyroid disease can mean either a much faster or much slower metabolism than normal. A person with increased thyroid function often also has protruding eyes and an enlarged thyroid gland (goiter).
• Adrenal gland (Addison's disease). The adrenal glands sit on top of each kidney and make several important hormones. Autoimmune disease against the adrenal glands often causes weakness, fatigue, nausea, and skin rashes.
• Skin (vitiligo). Autoimmune disease against the skin can cause irregular light patches on the skin.
• Neurotransmitters (myasthenia gravis). Autoimmune disease against certain neurotransmitters prevents nerve signals from reaching the muscles. This condition can lead to muscle weakness that gets worse with activity and improves with rest.
• Intestine and stomach (celiac disease, B12 deficiency). Autoimmune disease against the intestine and stomach can interfere with digestion and prevent a person from absorbing nutrients from food.

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Screening

Some researchers recommend that Type 1 diabetics and their families be screened yearly for thyroid function. This is particularly true for family members if the Type 1 diabetic has developed thyroid disease, which puts the family members at increased risk.

References

Betterle, C., et al. (1984). Clinical and subclinical organ-specific autoimmune manifestations in type 1 (insulin-dependent) diabetic patients and their first-degree relatives. Diabetologia, 26, 431-436.

Holl, R. W., et al. (1999). Thyroid autoimmunity in children and adolescents with type 1 diabetes mellitus. Effect of age, gender and HLA type. Horm Res, 52, 113-118.

Leong, K. S., et al. (1999). Clinical presentation of thyroid dysfunction and Addison's disease in young adults with type 1 diabetes. Postgrad Med J, 75, 467-470.

Maugendre, D., et al. (1997). Increased prevalence of thyroid autoantibodies and subclinical thyroid failure in relatives of patients with overt endocrine disease- associated diabetes but not type 1 diabetes alone. Diabetes Metab, 23, 302-307.