The antibodies anti thyroperoxidase thyroid (anti TPO antibodies or ab TPO) are gods autoantibodies, that is, antibodies directed against our organism, in this case against the enzyme thyroperoxidase or thyroid peroxidase.
Anti-thyroid peroxidase antibodies
The antibodies to thyroperoxidase, also called anti thyroid peroxidase antibodies, ab anti thyroid peroxidase, anti tpo, or abtpo, they target thyroid peroxidase (thyroid peroxidase), which is the key enzyme for the production of thyroid hormones (T4 or thyroxine and T3 or triiodothyronine) starting from thyroglobulin.
They are called autoantibodies, as they attack structures in our own body.
There thyroid peroxidase, or thyroid peroxidase, it is an enzyme that promotes the iodination of tyrosine to form monoiodotyrosine (MIT) and diiodiotyrosine (DIT), which join together to give rise to thyroid hormones.
Antibodies to thyroperoxidase, together with antibodies to thyroglobulin and TSH receptor antibodies, constitute the so-called thyroid antibodies, also called anti thyroid antibodies.
Autoantibodies to thyroperoxidase are very common in autoimmune diseases of the thyroid, in particular the Hashimoto's thyroiditis it is characterized by the positivity of antibodies to thyroperoxidase in more than 90% of the affected persons.
Another autoimmune disease, the Graves' disease is characterized by ab tpo positive in the 80% of cases it should also be said that antibodies to thyroperoxidase can be found in a small percentage of people with autoimmune diseases affecting organs other than the thyroid. In addition, about one in 10 healthy people have positive anti-thyroid peroxidase antibodies even in the absence of thyroid disease.
Finally, it can happen that these autoantibodies are measurable in the blood only after a certain period of time from the onset of the disease: in other words, a first check of antibodies to thyroperoxidase it can also be negative in the presence of autoimmune thyroiditis; in these cases, if the clinical suspicion is strong, this test must be repeated after a certain period of time to re-establish the positivity or confirm the negativity of the anti tpo autoantibodies.
The blood concentration of the antibodies to thyroid peroxidase the greater the likelihood of an autoimmune pathology affecting the thyroid gland, it is greater: there is therefore a certain relationship between the autoimmune activity responsible for the thyroid inflammatory process and the concentration of anti-thyroid peroxidase antibodies.
High thyroid peroxidase autoantibodies
Here are the causes of positivity of antibodies to thyroperoxidase, listed in order of frequency:
- Hashimoto's thyroiditis: also called lymphocytic thyroiditis or chronic autoimmune thyroiditis is a fairly common disease. It is probably the most frequent cause of hypothyroidism in adults. In the initial phase of Hashimoto's thyroiditis, thyroid function may still be normal, while in the later stages subclinical hypothyroidism usually develops initially and then overt hypothyroidism, with high TSH and low fT4. The diagnosis is obviously based on the clinic and on the finding of the presence of high antithyroglobulin and antiperoxidase antibodies in the circulation. The antibodies to thyroglobulin they tend to be taller in the early stages of the disease, and then drop in distance, while the antibodies to thyroid peroxidase they usually remain high for many years after diagnosis.
- Graves Basedow's disease: it is the most common cause of hyperthyroidism, often accompanied by goiter, ophthalmopathy (the typical "protruding eye") and rarely by dermopathy (myxedema at the pretibial level). Hyperplasia and overactivity of the thyroid are caused by circulating antibodies whose specific antigen is represented by the TSH receptor present on the surface of thyroid cells (thyrocytes). Anti TSH antibodies (anti TSH-R or TSH-R Ab) stimulate the thyroid to produce thyroid hormones in an exaggerated way. In this pathology, in addition to anti TSH antibodies, antibodies to thyroid peroxidase are found in over 3/4 of patients.
- Granulomatous thyroiditis: or De Quervain's thyroiditis, is a sub-acute inflammation of the thyroid gland, generally triggered by a viral infection, which leads to the development of a transient hyperthyroidism which then results in hypothyroidism. Clinically, the disease manifests itself with myalgia (muscle pain), pharyngitis, low fever and asthenia (fatigue). Later, if the fever persists, pain and swelling (swelling) in the neck may appear. In a modest percentage of cases there are antibodies to thyroglobulin e positive anti thyroid peroxidase.
- Sporadic thyroid goiter: it is the type of goiter that does not depend on environmental causes such as iodine deficiency (it is therefore not "endemic") but is caused by other factors such as thyroid pathologies or thyroid neoplasms.
- Rheumatological diseases: such as systemic lupus erythematosus (SLE), Sjogren's syndrome and rheumatoid arthritis.
- Immuno-haematological diseases: such as autoimmune hemolytic anemia, myasthenia gravis, pernicious anemia, and type 1 diabetes mellitus.
- Neoplasms: such as colon cancer or thyroid cancer.
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