Iodine deficiency is the most relevant etiologic factor in
endemic goiter. However, the fact that not all residents in the same area eventually develop
goiter suggests that individual factors might also be involved in the etiology of
endemic goiter. We have previously reported a point mutation in
thyroglobulin exon 10 associated with nonendemic
simple goiter. In an attempt to determine whether the mutation in
thyroglobulin exon 10 might be linked to
endemic goiter, we studied the genomic organization of
thyroglobulin exon 10 in 36 patients diagnosed with
endemic goiter by Southern blot, PCR, and sequencing analysis. We also analyzed by Southern blot the organization of the genomic region that contains
thyroglobulin exons 1 to 11. In one case, we observed a point mutation in
thyroglobulin exon 10. Sequencing analysis revealed a mutation at position 2610 of the
cDNA, which implies a G to T substitution. This single base change results in a
glutamine to
histidine substitution and is the same as that previously reported by our group in patients with nonendemic
goiter. To our knowledge, this is the first time that a mutation in the
thyroglobulin gene has been described in a patient with endemic
simple goiter and further confirms the association between the exon 10 mutation and development of
goiter.