Reykjavik-based Decode Genetics, which is a lot better at personal genomics than selecting investment advisors, is back in the news now that its scientists have determined that 57% of all thyroid cancer is attributable to 2 genetic variations.
Julius Gudmundsson and colleagues report in Nature Genetics that the variants are simple base-pair substitutions occurring in genes residing near those controlling thyroid gland development, one on Chromosome 9 and the other on Chromosome 14.
Compared with those having neither variant, “the risk associated with these variants was almost six-fold, which is quite extraordinary,” Erich Sturgis, a head and neck surgeon at Houston’s MD Anderson Cancer told the New York Times.
Each year in the US, about 35,000 cases of thyroid cancer are diagnosed. Treatment generally includes surgical resection of the gland followed by lifelong thyroid replacement. It’s quite effective and only 1,500 people die from thyroid cancer each year.
The Decode breakthroughs are thus not going to trigger interest in population-wide screening programs, but the information would be useful in the assessment of people at high risk, such as those with a positive family history of the disease.
Gudmundsson’s group reached its conclusions by performing a genome-wide association study involving 192 positive cases and a large control group.
They showed that people having both genetic variants had low levels of thyroid-stimulating hormone, which is produced normally by the pituitary gland.
TSH helps thyroid cells mature, so the authors postulate that chronically low TSH levels might impede their differentiation and thus increase the risk of malignant transformation.
If this theory proves correct, TSH supplementation might reduce the risk of developing thyroid cancer in affected individuals.