Significance Of Anti-Thyroperoxidase Antibody Estimation In Patients With Hypothyroidism

Introduction: Hypothyroidism is a common endocrine disorder characterized by decreased levels of thyroid hormones. Anti-thyroperoxidase antibody is produced in autoimmune thyroiditis which inhibits the synthesis of thyroid hormones. Aims & Objectives: The study was planned to explore the significance of anti-TPO antibody in hypothyroid patients. Materials and Methods: 150 newly diagnosed patients, age 20-60 years were enrolled for the study. Patients were divided on the basis of antiTPO levels as anti-TPO positive(n=87) anti-TPO negative (n=63).Thyroid hormones viz. serum triiodothyronine (T3), thyroxine (T4), free T3 (FT3), free T4 (FT4) and thyroid stimulating hormone (TSH) levels were compared between the two groups. Results: Mean serum TSH level was significantly higher in anti-TPO positive group. Mean serum T3 & T4 levels were comparable (P= NS) among the two groups whereas FT3 (P= 0.014) and FT4 (P= 0.003) were significantly lower in the anti-TPO positive group. Conclusion: Serum FT3 & FT4 represent the biologically active proportion of thyroid hormones. The present study suggests that lower FT3 & FT4 levels can better correlate with anti-TPO activity in patients of hypothyroidism

Learning from POSTAL study: can levothyroxine improve pregnancy outcomes in women with thyroid autoimmunity? / 中华内分泌代谢杂志

Whether levothyroxine ( LT4 ) treatment improves outcomes following in vitro fertilization and embryo transfer ( IVF-ET) in euthyroid women who have tested positive for thyroid autoantibodies remains unclear. In Pregnancy Outcome Study in enthyroid women with Thyroid Autoimmunity after Levothyroxine ( POSTAL) trial, which was a randomized controlled study involving 600 euthyroid women undergoing IVF-ET who were tested positive for thyroperoxidase antibodies, the miscarriage rate, clinical pregnancy rate and live-birth rate were not significantly different between the LT4 intervention group and control group. Therefore, LT4 treatment did not appear to improve pregnancy outcomes among women with thyroid autoantibodies undergoing IVF-ET.

The Changes of Expression of Thyroid Specific Antigens in Aging / 대한내분비학회지

BACKGROUND: With the prevalence of serum antithyroglobulin(anti-TG) and antithyroperoxidase(anti-TPO) autoantibodies increasing with age, it has been suggested that changes of thyroid autoimmunity with aging are associated with endemic iodine intake. To understand the mechanism of aging-related increases of thyroid autoimmune response, we investigated the expression of thyroid specific autoantigens of aged phenotype, and compared them with those of young phenotype both in vivo and in vitro. METHODS: Sprague-Dawley rats were sacrificed at 5, 10 and 16 weeks(young), and at 23 months(aged). Their FRTL-5 thyroid cells were harvested at cell passages less than 10(fresh) or more than 30 (aged). The expression of thyroid autoantigens, sodium-iodide symporter(NIS), TSH receptor (TSHR), TG and TPO, were examined by northern blot analysis. To evaluate the effects of iodide, 1mM of NaI was added to the medium for 24 hours, and following incubation the expressions of MHC class I and class II were also examined. RESULTS: The expressions of TPO were markedly increased in the aged rats, and those of TG were moderately. However, NIS and TSHR showed no differences in their expression levels between aged rats and young rats. In vitro, there were no differences in the expressions of TG or TPO, nor of NIS or TSHR, between aged cells and fresh cells. Neither did Iodide exhibit any influence on the expression of MHC molecules in aged cells or fresh cells. CONCLUSION: The expression levels of TPO and TG were increased in aged rats, which may partially explain the mechanism of increasing thyroid autoimmunity with age.

Autoantigenic Role of Variant Thyroperoxidase / 대한내분비학회지

Background: Thyroperoxidase(TPO) is one of the most important autoantigens in autoimmune thyroid disorders and autoantibody to TPO is found in almost every patients with various autoimmune thyroid diseases. Human TPO was already cloned and the completed nucleotide sequences are well known. In human thyroid tissues, several variants mRNA's of TPO are found in addition to the wild type. Especially the variants lacking exon 10(TPOΔexon10) and exon 16(TPOΔ exon16) are found in very large amount in both normal and Graves thyroid tissues. The significance of these variants TPO mRNAs are largely unknown. The authors tried to investigate the autoantigenic role of these variant TPO. Methods : To produce variant TPO cDNAs, oligonucleotide directed mutagenesis was performed using cDNA for wild type human TPO as template. The produced variants cDNAs were transfected into Cos-7 cells and variants TPO proteins were tested against patients sera showing high titers of anti-TPO antibody. Results: Seven of 12 Graves sera reacted with TPOΔexon 10 and 8 Graves sera with TPOΔ exonl6. Eight of 15 Hashimoto sera reacted TPOΔexon16 and 9 with TPOΔexon16. The reactivity with variants TPO was not related to clinical findings. Conclusion: These two variant TPOs, that is TPOexon10 and TPOΔexon16, could act as an autoantigen if they were translated in vivo, and could play a role in autoimmune thyroid disease. Their exact role in the pathogenesis of autoimmune thyroid disorders are to be clarified.