Does the Polymorphism in the Length of the Polyalanine Tract of Gene Influence the Risk of Thyroid Dysgenesis Occurrence?

Recent data have suggested that polymorphisms in the length of the polyalanine tract (polyA) of gene may act as a susceptibility factor for thyroid dysgenesis. The main purpose of this study was to investigate the influence of polyA of gene on the risk of thyroid dysgenesis. A case-control study was conducted in a sample of 90 Brazilian patients with thyroid dysgenesis and 131 controls without family history of thyroid disease. Genomic DNA was isolated from peripheral blood samples and the genotype of each individual was determined by automated sequencing. More than 90% of genotypes found in the group of patients with thyroid dysgenesis and in controls subjects were represented by sizes 14 and 16 polymorphisms in the following combinations: 14/14, 14/16, and 16/16. Genotypes 14/16 and 16/16 were more frequent in the control group, while genotype 14/14 was more frequent in the group of patients with thyroid dysgenesis. There was no difference between agenesis group and control group. Genotype 14/14 when compared to genotypes 14/16 and 16/16A showed an association with thyroid dysgenesis. PolyA of gene alters the risk of thyroid dysgenesis, which may explain in part the etiology of this disease.