The detection of somatic mutations of thyrotropin receptor gene in fine needle biopsy samples from thyroid nodules.

OBJECTIVE To evaluate the detection possibility of TSH receptor gene mutation within the third cytoplasmic loop and the sixth transmembrane domain in the cytological material obtained by means of fine needle biopsy of autonomous and non-autonomous nodules. METHODS The study has been carried out in 16 women with goitre showing no clinical signs of hyperthyroidism. According to the thyroid scintigraphy and serum level of thyrotropin (TSH) the patients were divided into two groups: 1. 6 patients with autonomous nodules; 2. 10 patients with non-autonomous nodules. Genomic DNA has been isolated from the cytological material and the peripheral blood nuclear cells in order to confirm possible somatic character of TSH receptor gene mutations. DNA has been amplified in polymerase chain reaction (PCR) with the use of a specific pair of primers. Purified PCR products have been subjected to further automatic sequencing. RESULTS Among 6 autonomous nodules tested one heterozygotic somatic mutation of adenine for cytosine at 1804 nucleotide of TSH receptor gene was detected. This mutation resulted in the change of threonine (codon ACC) at 632 position of TSH receptor protein for proline (codon CCC). Among the non-autonomous nodules one heterozygotic somatic mutation of adenine for cytosine at 1870 nucleotide of receptor TSH gene has been detected. From this mutation followed the change of lysine (codon AAG) at 624 position of the polypeptide chain for glutamine (codon CAG) followed as a consequence. CONCLUSIONS We emphasize the validity of fine needle biopsy in the detection of somatic mutations in the TSH receptor gene. For the first time the somatic mutation in the TSH receptor gene in a non-autonomous nodule has been reported.