Lab Test Allows Biennial Thyroid Disease Screen

WASHINGTON — Measures of thyroperoxidase autoantibody and thyroid-stimulating hormone once every 2 years are a reliable alternative to annual screens for thyroid disease in children with type 1 diabetes, Dr. Linda A. DiMeglio reported at the annual scientific sessions of the American Diabetes Association.

After thyroperoxidase (TPO) autoantibody results come back positive, thyroid-stimulating hormone (TSH) and thyroxine (T4) tests are performed annually.

Thyroid disease screening in children with diabetes often consists of annual TSH and T4 tests. Endocrinologists at the James Whitcomb Riley Hospital for Children in Indianapolis, decided to modify the protocol by using TPO testing, after the results of studies at their institution and others showed that elevated TPO levels were highly predictive of autoimmune thyroid disease, Dr. DiMeglio said.

Antibodies against TPO and thyroglobulin are found in approximately 10% of the general population and in up to 25% of people with type 1 diabetes, said Dr. DiMeglio of the Indiana University School of Medicine.

Although both are helpful in predicting the development of autoimmune thyroiditis in diabetic patients, “more patients with autoimmune thyroid disease have high TPO levels than have high thyroglobulin levels, and TPO levels correlate with the active phase of disease.”

Investigators at Riley Hospital did a retrospective study of 462 diabetic children (mean age of 13) who had both TSH and thyroid-specific autoantibodies measured. The prevalence of thyroid autoimmunity was approximately 20% and the prevalence of autoimmune thyroid disease was about 5%, she said.

“All the patients in this population who were diagnosed with autoimmune thyroid disease also had thyroid autoimmunity,” she said. Disease prevalence increased as autoantibody levels rose and as children got older.

More data are needed to predict the rate of progression from detection of autoimmunity to development of hypothyroidism. “The rate of decline in thyroid hormone secretion is slow, which is important to realize when you look at screening every 2 years versus annual screening,” Dr. DiMeglio said. “By doing TPO as an anticipatory measure and TSH as a point-in-time measure, it's unlikely that you'll miss kids who have developed severe hypothyroidism over the 2-year period.”

Endocrinologists at Riley Hospital now perform their first screening for TSH and TPO at the first visit after the diagnosis of type 1 diabetes. After TPO antibodies are detected, the endocrinologists are divided about whether to measure total or free T4 at annual testing for TSH and T4. “I prefer using a total T4, but some of my colleagues feel differently,” Dr. DiMeglio said.

Thyroid disease is difficult to diagnose clinically in diabetes. The presentation of hypothyroidism, in particular, can resemble that of nephropathy and neuropathy. And the symptoms of hyperthyroidism can be similar to those of poor glycemic control.

Hypothyroidism can directly affect the course of diabetes, reducing the insulin degradation rate and causing abnormalities in lipid metabolism such as elevated triglycerides and LDL cholesterol, Dr. DiMeglio said.

Hypothyroidism will affect 15%–30% of patients with diabetes over their lifetimes. As in the general population, thyroid disease is associated with increasing age, female gender, and white ethnicity.

Hyperthyroidism appears to affect people with diabetes at about the same rate as it does the general population, DiMeglio noted.

Although the TSH assay is the most reliable screening test for thyroid dysfunction of either type, “it's important to remember that it's not perfect,” and that poorly controlled diabetes can result in “inappropriately low” serum TSH concentrations, she said.

WASHINGTON — Measures of thyroperoxidase autoantibody and thyroid-stimulating hormone once every 2 years are a reliable alternative to annual screens for thyroid disease in children with type 1 diabetes, Dr. Linda A. DiMeglio reported at the annual scientific sessions of the American Diabetes Association.

After thyroperoxidase (TPO) autoantibody results come back positive, thyroid-stimulating hormone (TSH) and thyroxine (T4) tests are performed annually.

Thyroid disease screening in children with diabetes often consists of annual TSH and T4 tests. Endocrinologists at the James Whitcomb Riley Hospital for Children in Indianapolis, decided to modify the protocol by using TPO testing, after the results of studies at their institution and others showed that elevated TPO levels were highly predictive of autoimmune thyroid disease, Dr. DiMeglio said.

Antibodies against TPO and thyroglobulin are found in approximately 10% of the general population and in up to 25% of people with type 1 diabetes, said Dr. DiMeglio of the Indiana University School of Medicine.

Although both are helpful in predicting the development of autoimmune thyroiditis in diabetic patients, “more patients with autoimmune thyroid disease have high TPO levels than have high thyroglobulin levels, and TPO levels correlate with the active phase of disease.”

Investigators at Riley Hospital did a retrospective study of 462 diabetic children (mean age of 13) who had both TSH and thyroid-specific autoantibodies measured. The prevalence of thyroid autoimmunity was approximately 20% and the prevalence of autoimmune thyroid disease was about 5%, she said.

“All the patients in this population who were diagnosed with autoimmune thyroid disease also had thyroid autoimmunity,” she said. Disease prevalence increased as autoantibody levels rose and as children got older.

More data are needed to predict the rate of progression from detection of autoimmunity to development of hypothyroidism. “The rate of decline in thyroid hormone secretion is slow, which is important to realize when you look at screening every 2 years versus annual screening,” Dr. DiMeglio said. “By doing TPO as an anticipatory measure and TSH as a point-in-time measure, it's unlikely that you'll miss kids who have developed severe hypothyroidism over the 2-year period.”

Endocrinologists at Riley Hospital now perform their first screening for TSH and TPO at the first visit after the diagnosis of type 1 diabetes. After TPO antibodies are detected, the endocrinologists are divided about whether to measure total or free T4 at annual testing for TSH and T4. “I prefer using a total T4, but some of my colleagues feel differently,” Dr. DiMeglio said.

Thyroid disease is difficult to diagnose clinically in diabetes. The presentation of hypothyroidism, in particular, can resemble that of nephropathy and neuropathy. And the symptoms of hyperthyroidism can be similar to those of poor glycemic control.

Hypothyroidism can directly affect the course of diabetes, reducing the insulin degradation rate and causing abnormalities in lipid metabolism such as elevated triglycerides and LDL cholesterol, Dr. DiMeglio said.

Hypothyroidism will affect 15%–30% of patients with diabetes over their lifetimes. As in the general population, thyroid disease is associated with increasing age, female gender, and white ethnicity.

Hyperthyroidism appears to affect people with diabetes at about the same rate as it does the general population, DiMeglio noted.

Although the TSH assay is the most reliable screening test for thyroid dysfunction of either type, “it's important to remember that it's not perfect,” and that poorly controlled diabetes can result in “inappropriately low” serum TSH concentrations, she said.

WASHINGTON — Measures of thyroperoxidase autoantibody and thyroid-stimulating hormone once every 2 years are a reliable alternative to annual screens for thyroid disease in children with type 1 diabetes, Dr. Linda A. DiMeglio reported at the annual scientific sessions of the American Diabetes Association.

After thyroperoxidase (TPO) autoantibody results come back positive, thyroid-stimulating hormone (TSH) and thyroxine (T4) tests are performed annually.

Thyroid disease screening in children with diabetes often consists of annual TSH and T4 tests. Endocrinologists at the James Whitcomb Riley Hospital for Children in Indianapolis, decided to modify the protocol by using TPO testing, after the results of studies at their institution and others showed that elevated TPO levels were highly predictive of autoimmune thyroid disease, Dr. DiMeglio said.

Antibodies against TPO and thyroglobulin are found in approximately 10% of the general population and in up to 25% of people with type 1 diabetes, said Dr. DiMeglio of the Indiana University School of Medicine.

Although both are helpful in predicting the development of autoimmune thyroiditis in diabetic patients, “more patients with autoimmune thyroid disease have high TPO levels than have high thyroglobulin levels, and TPO levels correlate with the active phase of disease.”

Investigators at Riley Hospital did a retrospective study of 462 diabetic children (mean age of 13) who had both TSH and thyroid-specific autoantibodies measured. The prevalence of thyroid autoimmunity was approximately 20% and the prevalence of autoimmune thyroid disease was about 5%, she said.

“All the patients in this population who were diagnosed with autoimmune thyroid disease also had thyroid autoimmunity,” she said. Disease prevalence increased as autoantibody levels rose and as children got older.

More data are needed to predict the rate of progression from detection of autoimmunity to development of hypothyroidism. “The rate of decline in thyroid hormone secretion is slow, which is important to realize when you look at screening every 2 years versus annual screening,” Dr. DiMeglio said. “By doing TPO as an anticipatory measure and TSH as a point-in-time measure, it's unlikely that you'll miss kids who have developed severe hypothyroidism over the 2-year period.”

Endocrinologists at Riley Hospital now perform their first screening for TSH and TPO at the first visit after the diagnosis of type 1 diabetes. After TPO antibodies are detected, the endocrinologists are divided about whether to measure total or free T4 at annual testing for TSH and T4. “I prefer using a total T4, but some of my colleagues feel differently,” Dr. DiMeglio said.

Thyroid disease is difficult to diagnose clinically in diabetes. The presentation of hypothyroidism, in particular, can resemble that of nephropathy and neuropathy. And the symptoms of hyperthyroidism can be similar to those of poor glycemic control.

Hypothyroidism can directly affect the course of diabetes, reducing the insulin degradation rate and causing abnormalities in lipid metabolism such as elevated triglycerides and LDL cholesterol, Dr. DiMeglio said.

Hypothyroidism will affect 15%–30% of patients with diabetes over their lifetimes. As in the general population, thyroid disease is associated with increasing age, female gender, and white ethnicity.

Hyperthyroidism appears to affect people with diabetes at about the same rate as it does the general population, DiMeglio noted.

Although the TSH assay is the most reliable screening test for thyroid dysfunction of either type, “it's important to remember that it's not perfect,” and that poorly controlled diabetes can result in “inappropriately low” serum TSH concentrations, she said.