Similar prevalence of somatic TSH receptor and Gsalpha mutations in toxic thyroid nodules in geographical regions with different iodine supply in Turkey.
OBJECTIVE
Differences in iodine intake could account for the variable prevalences reported for somatic TSH receptor (TSHR) mutations in toxic thyroid nodules (TTNs). However, this question has not been settled, since no study has yet determined the TSHR mutation prevalence in regions with different iodine supplies in the same population using the same methodology. Therefore, we studied the prevalence of somatic TSHR mutations in TTNs from patients living in iodine-deficient or -sufficient regions in Turkey.


METHODS
We screened 74 TTNs for somatic TSHR mutations. Exons 9 and 10 of the TSHR and 7 and 8 of the Gsalpha were screened by denaturing gradient gel electrophoresis. Determination of X-chromosome inactivation was used for clonality analysis.


RESULTS
TSHR mutations were identified in 52 (70.2%) of 74 TTNs. A Gsalpha mutation was identified in one TTN. Three new TSHR mutations were detected (A627V, I640K, I486N). No significant difference between frequencies of TSHR mutations in iodine deficient/sufficient regions was found. The frequency of non-random X-chromosome inactivation was similar in iodine-sufficient or -deficient regions and in TSHR mutation positive or negative hot nodules.


CONCLUSIONS
These findings suggest that TTNs in iodine deficient/sufficient areas predominantly arise from aberrant growth of a single cell. Our results suggest that neither the prevalence of TSHR mutations nor that of monoclonal TTNs is related to iodine supply.
Gozu
Hulya Iliksu
HI
Section of Endocrinology and Metabolism, Dr. Lutfi Kirdar Kartal Education and Research Hospital, Turkey.
Bircan
Rifat
R
Krohn
Knut
K
Müller
Sandra
S
Vural
Selahattin
S
Gezen
Cem
C
Sargin
Haluk
H
Yavuzer
Dilek
D
Sargin
Mehmet
M
Cirakoglu
Beyazit
B
Paschke
Ralf
R
D000328:Adult; D000368:Aged; D004252:DNA Mutational Analysis; D005260:Female; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000235:genetics*; D005843:Geography; D006801:Humans; D007455:Iodine / Q000600:supply & distribution*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D018807:Polymorphism, Single-Stranded Conformational; D015995:Prevalence; D011989:Receptors, Thyrotropin / Q000235:genetics*; D016606:Thyroid Nodule / Q000453:epidemiology* / Q000235:genetics; D013971:Thyrotoxicosis / Q000453:epidemiology* / Q000235:genetics; D014421:Turkey / Q000453:epidemiology
D011989:Receptors, Thyrotropin; D007455:Iodine; D019205:GTP-Binding Protein alpha Subunits, Gs