Thyroid cancer occurs in 14 out of every 100,000 women per year in the U.S. compared to only five men per 100,000. And in 2008, there were 37,340 new cases of thyroid cancer and 1,590 deaths, according to the U.S. National Cancer Institute.
Scientists don’t know what causes the disease, but a new study out of Iceland suggests that two small mutations within the billions of total molecular units in our DNA may play some role. This is the first report of a genetic link specific to thyroid cancer.
The study led by Dr. Julius Gudmundsson and published in the journal Nature Genetics examined the DNA from more than 960 volunteers of northern European descent from Iceland, Spain and the US. The researchers found that having one of either two mutations slightly increased the risk of developing thyroid cancer by about 30%.
Having both mutations dramatically increased the risk. "When you take the risk of both of them, they have almost six times the risk of thyroid cancer that the average person has," said lead researcher Dr. Kari Stefansson, CEO of deCODE Genetics, the company that sponsored the research in Reykjavik, Iceland.
In the study, participants who had either mutation also tended to show altered blood levels of thyroid hormones or a decrease in thyroid stimulating hormone (THS) produced by the pituitary gland in the brain. This type of information helps scientists begin to understand the genetic and biological changes that may lead thyroid cancer, but more research is necessary before physicians can make predictions about who will get thyroid cancer solely based on these DNA mutation patterns.
"They have demonstrated that there is a relationship between these genes and thyroid cancer," states Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society. "But these mutations were also in a significant percentage of the control patients as well." One of the mutations was present in 35 percent of the population, and the other mutation was present in more than 50 percent of the population studied, Lichtenfeld noted.
For people who have a family history of thyroid cancer, however, the researchers believe a genetic test such as this may one day be particularly helpful. "This finding will lead to a wonderful diagnostic instrument that will allow us to develop a test to find people who are at an extraordinarily high risk of developing this disease," Stefansson said. "That is important, because if you diagnose thyroid cancers early, you have a very good chance of curing it," he said.
Gudmundsson, J., et al., 2009. “Common Variants on 9q22.33 and 14q13.3 Predispose to Thyroid Cancer in European Populations,” http://www.nature.com/ng/journal/vaop/ncurrent/abs/ng.339.html
HealthDay article, 2009. “Gene Test Could Predict Thyroid Cancer Risk,”
CancerNet, 2008. “Genetics of Thyroid Cancer,”
Cleveland Clinic, no date. “Genetics of Thyroid Cancer,” http://my.clevelandclinic.org/disorders/thyroid_cancer/hic_the_genetics_of_thyroid_cancer.aspx