Certain Thyroid-Related Diseases May Vary by Race
Study looked at Graves', Hashimoto's thyroiditis among U.S. military personnel
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.
However, Hennessey noted one problem with the study that may have caused researchers to undercount cases of thyroid disease.
The researchers relied on medical coding to identify cases of either Graves' disease or Hashimoto's thyroiditis. However, they did not include cases more generally coded as hyperthyroidism or hypothyroidism, and there's a chance the doctor who made the diagnosis overlooked Graves' or Hashimoto's as the underlying cause, he said.