Certain Thyroid-Related Diseases May Vary by Race
Study looked at Graves', Hashimoto's thyroiditis among U.S. military personnel
The analysis found that, compared to whites, black women are about twice as likely and black men are about two and a half times more likely to have Graves' disease.
Asian/Pacific Islander women had a 78 percent increased risk of Graves' disease compared to whites, while Asian/Pacific Islander men had a more than threefold increased risk, the study noted.
But the risk of Hashimoto's in both blacks and Asian/Pacific Islanders was much lower than the risk among whites, ranging from 67 percent to 78 percent less, the findings showed.
"The findings are striking, that there are so many more African Americans and Asian individuals who are coded as having Graves'," said Dr. James Hennessey, director of clinical endocrinology at Beth Israel Deaconess Medical Center in Boston. He was not involved with the new research.
Study author McLeod demurred when asked about how a person's race could influence their thyroid function.
"Our current study can't answer whether racial differences in autoimmune thyroid disease incidence are due to genetics, environmental exposures or a combination of both," McLeod said. "Further work needs to be performed to find the underlying mechanisms of thyroid autoimmunity."
In the paper, the researchers rule out one potential environmental influence -- smoking.
Smoking is associated with an increased risk for Graves' and a decreased risk for Hashimoto's. But whites have the highest smoking rates in the U.S. military, which runs counter to their increased risk for Hashimoto's and lower risk for Graves', the study authors added.
Hennessey of Beth Israel said he suspects that genetics are a likely culprit.
"Both of these conditions are autoimmune conditions that are known to be influenced by genetic factors, and those genetic factors may be clustered more in people depending on their race," Hennessey said.
The results of the study mirror other reports that have found elevated levels of thyroid-stimulating hormone in whites, Hennessey said. This hormone is produced by the pituitary gland and prompts the thyroid to release its own hormones into the blood.
"It sort of explains some findings we already had known, that thyroid function tests are different depending on race," he said.