Interestingly, the S836S minor allele (T allele) which was found to be associated with PTC in our study, was previously found to be over-represented in patients with MTC [10] and under-represented in patients with Hirschsprung disease [25], and these disorders are known to be caused by RET overactivity and underactivity, respectively. Here, RET is linked to medullary thyroid gland carcinoma.