European Journal of Molecular & Clinical Medicine

Abstract

The thyroid peroxidase (TPO) is a 105 kDa glycoprotein enzyme and the main antigen of the
thyroid microsomal fraction. It catalyses iodine oxidation and thyroglobulin tyrosyl iodination
reactions in the thyroid gland. Anti-TPO antibodies activate complement and are thought to be
significantly involved in thyroid dysfunction and the pathogenesis of hypothyroidism. These
antibodies are significantly present in patientsof Hashimoto's thyroiditis,Gravesdisease and
even in non-thyroidal conditions such as diabetes. In sub-clinical hypothyroidism (SCH),
presence of these antibodies is associated with increased risk of developing overt
hypothyroidism (OH). In the present study, anti-TPO antibodies were tested on 33 individuals,
all of whom reported thyroid stimulating hormone (TSH) levels > 6μIU/mL. These included
18 with SCH and 15 with OH.Anti-TPO ab positivity (levels > 28.4 IU/ml) was observed in 17
patients (51.5%) which included 5 with SCH and 12 with OH. There was greater prevalence of
positivity in OH compared to SCH (80% vs 27.8%). 8 of 33 subjects (24%) had significantly
raised anti-TPO ab (>200 IU/ml). The Billewicz scoring system was used for assessment of
clinical features of hypothyroidism with value ≥25 strongly suggestive of OH. 9 of 33 subjects
had scores ≥25 and out of these, 7 had positive anti-TPO ab.Pearson correlation revealed the
serum TSH and anti-TPO levels to be strongly positively correlated, r(32) =
.7902, p <0.0001.The Billewicz diagnostic score was also correlated with anti-TPO levels, r(32)
= .4107 which was significant at p<0.05.Our results show that higher anti-TPO ab and
TSHlevels are associated with higher symptom scores, indicating underlying
pathophysiological and immunological processes and we suggest that antibodies against TPO
should be routinely assessed in patients presenting with either elevated TSH levels or with
symptoms suggestive of thyroid dysfunction.