|Year : 2013 | Volume
| Issue : 2 | Page : 74-77
A hospital-based study of anti-TPO titer in patients with thyroid disease
E Jacob Jeena1, M Malathi1, K Sudeep2
1 Department of Biochemistry, Father Muller Medical College, Kankanady, Mangalore, Karnataka, India
2 Department of Endocrinology, Father Muller Medical College, Kankanady, Mangalore, Karnataka, India
|Date of Web Publication||16-Sep-2013|
Department of Biochemistry, Father Muller Medical College, Kankanady, Mangalore - 575 002, Karnataka
Source of Support: None, Conflict of Interest: None
Context: Autoimmunity against the thyroid gland is one of the most important causes for thyroid dysfunction. Anti-thyroid antibody test is an important tool in the evaluation of autoimmune thyroid disorders. Aims: To study the prevalence of thyroid hormone dysfunction and positive anti-TPO antibody titers in patients being evaluated for thyroid-related disorders. Settings and Design:This retrospective cross-sectional study was done in Father Muller Medical College. Materials and Methods: The TSH (Thyroid stimulating hormone), FT 4 (Free thyroxine), and anti-TPO titer reports of 74 subjects undergoing evaluation for thyroid-related disorders were analyzed. Statistical Analysis Used: Statistical significance was estimated by P value. Results: About two-third (60%) of hypothyroid patients showed raised TPO antibody titer. The titer was significantly higher in hypothyroid subjects when compared to the euthyroid subjects, and a majority of the hypothyroid subjects had a titer at least twice the upper limit of normal. Two of the three subjects with hyperthyroidism also had elevated anti-TPO titers. Conclusions: The commonest cause of hypothyroidism in our study subjects was autoimmune-related thyroid disease. Anti-TPO antibody estimation is a very useful test for establishing the etiological diagnosis of autoimmune thyroid diseases in our population. In situations where there is a diffuse non-progressive goiter, anti-TPO antibody estimation can substitute for an invasive FNAC.
Keywords: Anti-thyroperoxidase antibodies, autoimmune thyroid disease, thyroid-stimulating hormone
Key Messages: Anti-TPO antibody estimation is a very useful test for establishing the etiological diagnosis of autoimmune thyroid diseases. In certain situations it is an effective substitute for an invasive fine needle aspiration
|How to cite this article:|
Jeena E J, Malathi M, Sudeep K. A hospital-based study of anti-TPO titer in patients with thyroid disease. Muller J Med Sci Res 2013;4:74-7
|How to cite this URL:|
Jeena E J, Malathi M, Sudeep K. A hospital-based study of anti-TPO titer in patients with thyroid disease. Muller J Med Sci Res [serial online] 2013 [cited 2019 Jul 22];4:74-7. Available from: http://www.mjmsr.net/text.asp?2013/4/2/74/118228
| Introduction|| |
Autoimmune thyroid disease is one of the common organ-specific autoimmune disorders. It is seen more commonly in women when compared to men.  About 2% to 4% of women and up to 1% of men are affected worldwide and the prevalence increases with advancing age.  Immunological alterations in thyroid follicular cells are attributed to the antibodies circulating against a wide range of thyroid antigens, among which thyro-peroxidase (TPO), thyroglobulin (TG), and TSH receptors are the most relevant antigens. Detection and quantification of the antibody titers help in establishing an autoimmune etiology.
To study the prevalence of thyroid hormone dysfunction and positive anti-TPO antibody titers in patients being evaluated for thyroid-related disorders.
| Materials and Methods|| |
The results of those patients whose antibody levels have been assayed were analyzed in this study. The assay for anti-TPO antibodies was recently introduced in Father Muller Medical College Hospital. It is an immunoassay based on the principle of electro-chemiluminescence using Elecsys 2010 auto analyzer. The upper limit of the normal range for anti-TPO is >33 IU/ml.
TPO assay results may get affected by interfering factors like Streptavidin, Ruthenium and the presence of high titers of antibodies to analyte specific antibodies in patient's serum. Thyroid anti-TPO antibodies have high specificity in determining autoimmunity against the thyroid antigens. TSH, free T4 were estimated by chemiluminescence.
Descriptive statistics for central tendency and dispersion were done using Microsoft Excel.
Results were divided into 3 groups; 47 cases of hypothyroidism, 3 cases of hyperthyroidism, and 24 euthyroid cases.
| Results|| |
The results of 74 subjects were analyzed. Their average age was 37.16 years (range 17- 80). Most of them were females (79%) [Table 1]. Of the total 74 subjects, 47 had hypothyroidism (64%), 24 were euthyroid (32%), and only 3 (4%) were hyperthyroid. Among the 59 females, 35 were hypothyroid and 23 were euthyroid. Among the 15 males, 12 were hypothyroid and 2 were hyperthyroid. The mean anti-TPO antibody level estimated in euthyroid subjects was 80 IU/ml [Table 2]. Of the total 47 hypothyroid subjects, 28 (60%) had raised TPO antibody titer (>33 IU/ml) with a mean of 471.825 (range 43.15-3000 IU/ml) while the rest had normal anti-TPO levels. Among the 28 hypothyroid subjects with positive antibody test, 21 (75%) had an antibody titer at least twice the upper limit (>68 IU/ml). Two out of 3 hyperthyroid subjects had positive antibody test with a titer twice the upper limit. Out of the 24 euthyroid subjects, 6 (25%) had elevated anti-TPO.
|Table 2: Mean, range, and standard deviation values of TSH, age, and anti-TPO parameters among euthyroid and hypothyroid groups|
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| Discussion|| |
Autoimmune thyroid diseases occur due to immune-mediated alterations in the thyroid gland, which produces functional alterations in the thyroid hormone status. Transient phases of hyperthyroidism and/or hypothyroidism occur in sub-acute thyroiditis, which commonly occurs due to destruction of the thyroid follicular cells. Chronic thyroid dysfunction i.e. hyperthyroidism (Grave's disease) and hypothyroidism (Hashimoto's Thyroiditis) occur secondary to the actions of antibodies. , Anti-TPO antibodies are the most prevalent and is present in 80-90% of Hashimoto's Thyroiditis, 65-75% of Grave's disease and 10-20% of nodular goiter or thyroid carcinoma. Even 10-15% of normal individuals can have an elevated antibody titer.  Thyroperoxidase (TPO) is a glycoprotein enzyme located in the thyrocyte membranes catalyzing the oxidation of iodide on tyrosine residues in thyroglobulin to yield triiodothyronine and thyroxine. Anti-TPO antibodies are cytotoxic, and they damage the thyroid cell by complement activation and antibody - dependent cell cytotoxicity.  Detection of these antibodies in significant titers helps in establishing the etiology of both hypo and hyper functioning thyroid diseases. , The antibody titers vary among individuals depending on the activity of the underlying auto immune activity. During the active phase of chronic lymphocytic thyroiditis, a high titer can be detected in the serum. Conversely, around 10-15% patients may have a negative antibody screening result in spite of the presence of an autoimmune process in the thyroid. The initiation of autoimmunity may be predisposed by genetic factors,  advancing age, environmental factors  such as stress,  infections,  trauma, smoking,  female  sex indicating hormonal influences, , and iodine  play a key role in the manifestation of autoimmune thyroiditis.
In our study, a majority of hypothyroid subjects had an elevated TPO antibody titer. Among those, who were negative for anti-TPO antibodies, there is a possibility of some of them would still have a cytological evidence of autoimmune destruction. As expected, there were more females (75%) with hypothyroidism. When compared to males, a larger number of females were found in the euthyroid group also. This shows that a larger number of females present clinically with thyroid-related symptoms than males. Almost all the males had evidence of thyroid dysfunction in our study. There were only three subjects with thyrotoxicosis and hence cannot be commented upon.
The high antibody titers in some of them reflect the active autoimmune process going on in the thyroid gland. About 75% of our antibody-positive hypothyroid subjects had a titer more than twice the upper limit of normal establishing a definitive autoimmune etiology. Also, 6 of our euthyroid subjects had positive antibody titers. This may be due to well-compensated thyroid function at present with a future risk of dysfunction in them. But, this high prevalence (25%) of positive antibody titer in euthyroid subjects reflects a referral bias, as this sampling was done on subjects attending a tertiary care hospital.
Most of the existing studies with a few exceptions have shown a positive correlation between antibody positivity and hypothyroidism. Vaseghani et al. concluded from their study that anti-TPO antibody titer correspond to TSH titers.  Studies done including one in Greece showed that all patients with sub-clinical hypothyroidism had positive anti-thyroid antibodies, , while some studies did not show significant difference. , A significant correlation between TSH or T4 concentration and elevated anti-TPO antibody was demonstrated by Ghoraishian et al. 
Fine needle aspiration cytology (FNAC) has a very good sensitivity for diagnosing Hashimoto's thyroiditis. However, those with focal lesions of Hashimoto's thyroiditis are likely to be missed. Also, some of the cytopathological features may overlap with other lesions like Hurthle cell neoplasm, reactive lymph node, and lymphoma. Also, a successful FNA requires adequate and representative sample being aspirated and an equally important expertise in interpretation. The acceptance of an invasive test like FNAC is not universal as a significant number of patients are wary about the pain and discomfort.
In suspected thyroid disorders, assessment begins with the evaluation of the thyroid hormone levels. In case of hypothyroidism, the presence of anti-TPO antibodies provides an etiological diagnosis. Anti-TPO antibodies are present in 60-65% of Grave's disease, but it is the presence of anti-TSH receptor antibody that is specific for autoimmune thyrotoxicosis. Anti-TPO antibodies, however, can be negative in 10-15% of individuals, which occurs when the autoimmune activity has subsided. In persons suspected to have other autoimmune diseases, anti-TPO antibodies can be used as a surrogate marker for the presence of autoimmunity.
Our study is limited by referral bias and small sample size. It is a cross-sectional analysis of results. A larger study with clinical and FNAC correlation is required to validate this test in our population.
| Conclusion|| |
The commonest cause of hypothyroidism in our study subjects was autoimmune-related thyroid disease. Anti-TPO antibody estimation is a very useful test for establishing the etiological diagnosis of autoimmune thyroid diseases in our population also. In situations where there is a diffuse non-progressive goiter, anti-TPO antibody estimation can substitute for an invasive FNAC.
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[Table 1], [Table 2]
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