Scientists at deCODE Genetics and academic collaborators from Iceland, the USA, The Netherlands and Spain has reported the discovery of three variants in the human genome that associate with levels of thyroid stimulating hormone and risk of thyroid cancer. The paper ‘Discovery of common variants associated with low TSH levels and thyroid cancer risk‘ is published on the online edition of Nature Genetics.

Using data obtained by applying both Illumina whole-genome sequencing technology and Illumina SNP chip technology, deCODE’s scientists performed a genome wide association study on levels of thyroid stimulating hormone (TSH) in 27,758 Icelanders. 22 SNPs with genomewide significance were discovered, of which one, rs965513 had previously been shown to associate with thyroid cancer. The remaining 21 SNPs were genotyped in 561 Icelandic thyroid cancer cases and 40,013 controls.  Variants suggestively associated with thyroid cancer were then genotyped in an additional 595 non-Icelandic cases and 2,603 controls.

After combining the results, three separate variants on chromosomes 2q35, 8p12 and 14q13.3 were shown to associate with risk of thyroid cancer, conferring an added risk of 30 – 100%, compared to the general population.  These variants were also found to associate with low levels of TSH, a key regulator in the biology and endocrinology of the thyroid gland.

“This study underscores the important role that the genetics of diversity in normal physiologic function can play in understanding the risk of disease. To date, the at-risk alleles of all the variants that confer risk of thyroid cancer associate with decreased serum levels of TSH, suggesting that the primary disorder in non-medullary thyroid cancer is an endocrine one, characterized by decreased concentration of TSH,” said Kari Stefansson, deCODE’s CEO and senior author of the study.

Thyroid Cancer is a malignant thyroid neoplasm, which can be treated with radioactive iodine or surgical resection of the thyroid gland. The contribution of genetics to the risk of thyroid cancer is greater than to any other cancer. Thyroid cancer is classified into four main histology groups: papillary (PTC), follicular (FTC), medullary (MTC), and undifferentiated or anaplastic thyroid carcinomas.  The great majority of malignant thyroid tumours are nonmedullary, either PTC (80–85%) or FTC (10–15%).