Abstract

OBJECTIVE: Subclinical hypothyroidism (SCH) is defined as high levels of TSH in the presence of normal levels of serum FT4. Since thyroid peroxidase (TPO) plays a key role in thyroid hormone synthesis, variations in the TPO gene can change the enzyme structure and result in the production of anti-TPO antibodies. The aim of this study was to examine the relationship between the Asn698Thr (A2095C) and Thr725Pro (A2173C) polymorphisms of the TPO gene and anti-TPO levels in patients with SCH. DESIGN: In this study, 150 individuals (75 cases and 75 controls), aged 19-75 years, were selected randomly by a clinician. The thyroid function tests included were FT3, FT4, TSH and anti-TPO antibodies using EL ISA. The TPO gene polymorphisms were examined by PCR-RFLP. RESULTS: Anti-TPO levels in the experimental group was significantly increased (P=0.020). The A2095C genotype frequency in the experimental and control groups were 37.3 vs 34.7 for the AA healthy genotype, 20 vs 46.7 for AC and 42.7 vs 18.6 for CC, respectively (P=0.001). The A2173C genotype frequency in the experimental and control groups were 22.6 vs 68 for healthy AA, 40 vs 25.3 for AC and 37.4 vs 6.7 for CC, respectively (P <0.001). The increased anti-TPO antibodies were significantly associated with the A2173C polymorphism (P=0.035). The findings showed that the chance (odds ratio) of developing subclinical hypothyroidism in individuals who had C alleles was 1.5 and 5.6-fold higher than in individuals without these alleles in the A2095C and A2173C regions, respectively. CONCLUSIONS: Determination of anti-TPO antibody levels and exon 12 TPO gene polymorphisms in patients with SCH can be helpful for prediction of overt hypothyroidism.