Forty eight DNA samples from 31 toxic goiter patients and 17 thyroid cancer patients were analyzed to detect g.IVS5+1G>A, g.IVS34-1G>C and c.886C>T mutations of the thyroglobulin (TG) gene. Among these samples three homozygous mutations were detected. Two of these mutations were detected in two toxic goiter patients as guanine to adenine transition g.IVS5+1G>A at position +1 of the donor splice acceptor site in exon-intron 5 and transversion that replaced guanine by cysteine (g.IVS34-1G>C) in the exon 34. The third homozygous mutation was detected among one thyroid cancer patient as transition that replaced cysteine by thymine c.886C>T in the exon 7. No homozygous g.IVS34-1G>C mutation was detected in thyroid disorders before, to our knowledge this is the first time by which homozygous mutation was detected in one toxic goiter patient.