Thyroid cancer co-occurs with Hashimoto's thyroiditis more often than with Graves' disease

Individuals with autoimmune thyroid diseases tend to have a higher risk of developing cancer of the gland, which is one reason why researchers at Japan's Ito Hospital recently tabulated the incidence of thyroid tumors among patients with Graves' disease (GD) or Hashimoto's thyroiditis (HT).

Their results, which appeared in the journal Thyroid, indicated that people with HT are at approximately twice the risk of being diagnosed with papillary thyroid cancer, compared to those with GD.

Likewise, participants with HT were more likely to have benign thyroid adenomas, with advanced age being an especially strong risk factor.

Also known as chronic lymphocytic thyroiditis, HT is an autoimmune disease that affects between 0.1 and 5 percent of adults in all Western nations, the National Institutes of Health (NIH). states.

Of all the causes of hypothyroidism - a condition in which the gland underproduces thyroid hormones - HT is the most common, according to the National Institute of Diabetes and Digestive and Kidney Diseases.

By contrast, GD is the most widespread cause of hyperthyroidism, a disease characterized by excess levels of thyroid hormones. The NIH estimates that 2 to 3 percent of Americans have GD.

In the new study, researchers used ultrasound imaging and fine-needle biopsies to check more than 3,600 patients with HT or GD for thyroid cancer.

Overall, they found that 1.77 percent of patients with HT tested positive for papillary thyroid cancer, whereas 0.97 percent of participants with GD were diagnosed with it.

Of the remaining 998 patients that were found to have benign thyroid nodules, known as adenomas, nearly one-half were over the age of 60.

The study's authors concluded that individuals who are known to have autoimmune thyroid diseases like HT or GD should be checked for the presence of thyroid cancer if they are found to have lumps, lesions or adenomas of the gland.