The antibodies to thyroglobulin, also called anti-tgb, TgAb, anti-htg or anti-tg antibodies, are antibodies directed against thyroglobulin, a precursor of thyroid hormones. Anti-thyroglobulin antibodies belong to the group of thyroid autoantibodiesio anti thyroid antibodies, together with antibodies thyroid antioxidase and ai TSH antibodies. They are very common antibodies in autoimmune thyroid diseases such as Hashimoto's thyroiditis and Graves-Basedow's disease.
Thyroglobulin antibodies normal values
Reference values for thyroglobulin antibodies are from 0 to 115 IU / ml, regardless of gender.
The thyroid autoantibodies they are antibodies that, instead of attacking a substance or a foreign organism to our body, attack components of the thyroid. They are formed when our immune system reacts against certain components of the thyroid gland or against thyroid proteins, causing a phlogosis (inflammation) of the thyroid gland (defined by the term of thyroiditis), causing damage to the thyroid tissues up to altering their functionality.
There thyroid it is a small, butterfly-shaped gland placed against the trachea in the anterior region of the neck. The thyroid, stimulated by TSH (thyrotropic hormone or thyrotropin), produces thyroid hormones, i.e. triiodothyronine (T3) and thyroxine (T4), which are responsible for the correct use of energy and a balanced metabolism of our body.
In the presence of anti-thyroid antibodies, the gland can be attacked and damaged in some of its components, and consequently autoimmune diseases associated with thyroid dysfunction can arise, which can be characterized by reduced function, i.e. hypothyroidism, both from a glandular hyperfunction, or from hyperthyroidism.
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Thyroid autoantibodies commonly sought are:
- Thyroglobulin antibodies (anti Tg): antibodies directed against thyroglobulin, a precursor of thyroid hormones.
- Thyroid peroxidase antibodies (anti TPO): antibodies directed against an enzyme responsible for the formation of thyroid hormones starting from iodine, thyroperoxidase.
- Antibodies to TSH receptors (anti rTSH): are antibodies that bind to the receptor present in the thyroid cells that normally binds thyrotropin. In turn, they break down into receptor-stimulating antibodies and receptor-inhibiting antibodies.
What are thyroglobulin antibodies? The thyroglobulin autoantibodies they are autoantibodies directed against thyroglobulin.
There thyroglobulin is the glycoprotein molecule, deriving from tyrosine, precursor of the thyroid hormones T3 and T4, or triiodothyronine and thyroxine, hormones that are synthesized starting from iodine thanks to the thyroid peroxidase enzyme.
High thyroglobulin antibodies
The antibodies to thyroglobulin they are present in many thyroid diseases. Here are the best known, listed in descending order of frequency:
- Hashimoto's thyroiditis (60% of cases): Hashimoto's thyroiditis is the most frequent of the thyroid diseases, it is caused by an activation of a particular type of white blood cell, the T helper lymphocytes, by the thyroid cells (thyrocytes), with production of cytokines (pro-inflammatory substances) that trigger an inflammatory process in the gland. Given that thyroid function sometimes remains normal, Hashimoto's thyroiditis can be characterized by a phase of transient hyperthyroidism, and by a subsequent state of hypothyroidism (subclinical or overt). The therapy consists of the administration of replacement therapy (usually Levothyroxine) in the case of a state of hypothyroidism. Hashimoto's thyroiditis is characterized in 90% of cases by antibodies to thyroid peroxidase, and in 50-60% of cases by positive thyroglobulin antibodies.
- Graves-Basedow disease (about 30% of cases): Graves' disease, also called diffuse toxic goiter, is an autoimmune disease affecting the thyroid gland. It is caused by antibodies stimulating the TSH receptor (one of the two variants of the TSH receptor antibodies), which cause overproduction of thyroid hormones and hyperthyroidism. Graves' disease can also be characterized by goiter thyroid, eye disease (ophthalmopathy) and skin changes (infiltrative dermopathy especially pretibial). In 30% some cases are found anti-Tg antibodies. The therapy is linked to the control of thyroid hyperfunction, which can be carried out through medical therapy (for example with the classic Tapazole, Thiamazole), radioactive iodine therapy and finally surgical therapy.
- Idiopathic myxedema of the adult: caused by the typical infiltrating dermopathy and by the presence of anti-TPO antibodies, by antibodies blocking the TSH receptor and, occasionally, by antibodies to thyroglobulin.
- Postpartum thyroiditis: malfunction of the thyroid gland which usually occurs within 12 months of childbirth and affects on average 5% in women (up to 20% in women who also have type 1 diabetes mellitus). The pathology is linked to the fact that, while during pregnancy there is a state of relative "immunosuppression", immediately after childbirth a condition develops with greater activation of the immune system, with manifestation of autoimmune phenomena, sometimes never previously highlighted. It manifests itself with an initial phase of hyperthyroidism, followed by hypothyroidism and finally a "restitution ad integrum" (restoration of normal thyroid function) in over 50% of cases. In a fair percentage of cases it is also characterized by antibodies to thyroglobulin.
- De Quervain's subacute thyroiditis: sub acute thyroiditis, usually following a viral infection. It is characterized by an important rise in the indices of PCR and ESR inflammation, and by the finding, especially in the early stages of the disease, of thyroid autoantibodies, although the latter do not appear to play an active role in the development of thyroiditis.
- Thyroid Cancer: in neoplasms of the thyroid, especially in the most frequent, namely the papillary carcinoma (or papillifero) and the follicular carcinoma thyroid gland, the presence of antibodies anti thyroglobulin makes the follow-up with thyroglobulin dosage problematic, as auto-antibodies bind to thyroglobulin, falsifying the dosage. Thyroglobulin antibodies are present in 15-20% of non-medullary thyroid cancer cases.
- Thyrotoxicosis: in a modest percentage of cases, there may be non-specific detection of anti-thyroglobulin antibodies positive even in the presence of hyperthyroidism with causes other than the aforementioned Graves-Basedow disease and Hashitoxicosis (i.e. the hyperthyroid phase in the course of Hashimoto's thyroiditis). The other most frequent reasons for hyperthyroidism are uninodular (Plummer's disease) and multinodular toxic goiter.
The antibodies elevated anti thyroglobulin can also be found in non-thyroid pathological conditions such as:
- Systemic lupus erythematosus (SLE): it is a chronic autoimmune disease, which affects women in 90% cases, at least in part hereditary (ie the affected people will more frequently have a relative in turn affected by SLE). Lupus is characterized by a variety of symptoms, depending on which organ is affected. Various types of autoantibodies are found in people affected by SLE, the most frequent are ANA (anti-nuclear antibodies), ENA (antibodies to extractable nuclear antigens, and anti-phospholipid antibodies (anti-cardiolipin antibodies, anti-beta-2 antibodies) glycoprotein-1, lupus anticoagulant). Often there are also associated autoimmune thyroid diseases, especially Hashimoto's thyroiditis and Graves-Basedow disease, with associated thyroid autoantibodies (anti-TPO, anti-rTSH and anti-TG). In a fair number of cases, antibodies to thyroperoxidase and antibodies to thyroglobulin can also be found even in the absence of thyroid diseases: in these cases, it is a non-specific finding, which will only require periodic TSH monitoring.
- Rheumatoid arthritis: is a chronic arthritis of autoimmune origin, which mainly affects the synovial joints. The blood tests show a positive result anti-citrulline antibodies he was born in rheumatoid factoris. In a small percentage of cases there is also the positivity of antibodies to thyroglobulin.
- Type diabetes mellitus THE: shape of diabetes which occurs mainly in the period of childhood and adolescence, with a strong autoimmune genesis. It has been demonstrated that in people with type 1 diabetes mellitus, the percentage of positivity for antibodies to thyroglobulin is increased compared to healthy people.
- Atrophic gastritis: autoimmune disease characterized by inflammatory changes of the gastric mucosa, with secondary atrophy and risk of gastrointestinal metaplasia. At the plasma level it is usually characterized by the presence of intrinsic factor antibodies, anti-proton pump antibodies, gastrin receptor antibodies. They rarely associate with antibodies to thyroglobulin, even in the absence of concomitant thyroid pathologies.
- Pernicious anemia: anemia (presence of low hemoglobin) characterized by a defect in the absorption of vitamin B12 due to a reduced production of intrinsic factor, secondary to the atrophy of the glandular mucosa of the stomach. Even in this autoimmune disease, there are often detectable autoantibodies in the blood, including gli ab anti Tg.
- Addison's disease: Addison's disease causes a reduced or absent function of the adrenal gland (in particular the part adrenal cortex), leading to the development of hypoadrenalism. This can be due to the destruction of the adrenal gland or its surgical removal, a defect in the production of adrenal hormones (steroidogenesis defect), or even an inadequate development of the gland. In the past, tuberculous infection also played an important role among the causes of hypoadrenalism. Often Addison's disease is associated with other autoimmune diseases, in the context of autoimmune polyglandular syndromes (polyglandular autoimmune syndromes, PGA) with the presence of autoantibodies in blood tests, including antibodies to thyroglobulin.
- Pregnancy: as already mentioned, often at the end of pregnancy, a state of "immunological tolerance" also ends and instead an overall activation of the immune system is established, with the consequent appearance of antibodies also directed towards the organism itself. Among the thyroid autoantibodies in a modest percentage of cases there may be the finding of antibodies to thyroglobulin, in the absence of impaired thyroid function.
Tags: Laboratory medicine Blood