Thyroglobulin (hTg), a glycoprotein with a molecular weight of about 660,000 Daltons, is the thyroid?s main iodine protein and the most important compound of follicular colloid. Thyroglobulin is the form under which the active hormones T3 and T4 together with their immediate forerunners MIT and DIT are laid inside the thyroid gland. The clinical applications of the hTg dosage seem to originate from its specificity for the thyroid and related cells.
The dosage of hTg can be used as support to scintigraphies or other techniques for studying pathogenesis, making a diagnosis and analyzing the course of thyroid disorders.
The dosage of hTg before and after replacement treatment with L-Thyroxin cannot be established in cases of hypothyroidism due to thyroid agenesis. In cases of secondary hypothyroidism with a dysglandular goiter or ectopic thyroid, the levels of hTg are normal or high. The circulating levels of hTg tend to increase in several thyroid disorders such as toxic and atoxic goiter, subacute thyroiditis, Basedow?s disease and carcinoma. In Basedow?s disease the hTg dosage is a potentially interesting index of normalization of hyperthyroidism in patients treated with anti-thyroid drugs. In the oncology field and more specifically for differentiated thyroid carcinoma, there are very promising applications linked to the ability of thyroid tumors tissues to concentrate iodine and synthesize hTg as a normal thyroid. Basically the dosage of hTg can be used as follows:

a. Pre-operating diagnosis of thyroid tumors. This application does not allow the differentiated diagnosis of the tumor as the values of hTg seen in malignant and benign nodules are superimposable.

b. Post-operation monitoring In patients treated surgically or with radiotherapy, long lasting hTg levels suggest the presence of a residual carcinoma and/or carcinoma with metastasis.

c. Monitoring of totally thyroidectomized patients The use of circulating hTg as an indicator of recurrent tumors (metastasis marker) has an established clinical value: the increase of Thyroglobulinaemia indicates the need to undergo further analysis for confirming the diagnosis. Interesting advantages can come from: a) a reduced use of scintigraphic diagnostic techniques as they imply regular suspension of replacement treatment and frequent exposure to radiation, b) and complete completion of the information obtained via scintigraphy.

Thyroglobulin ELISA:

Immunoenzymatic colorimetric method (ELISA) for quantitative determination of Thyroglobulin in serum.

Principle of the Assay:  

Four different anti-Thyroglobulin monoclonal antibodies are used. Three antibodies are coated on the wells; the fourth is soluble and conjugated to Biotin. Thyroglobulin in samples and standards binds to the immobilised antibodies on the surface of the microtiter wells and the second, soluble anti-Thyroglobulin antibody conjugated with biotin binds to the immobile antibody-Thyroglobulincomplex during the first incubation. After a washing step Streptavidin conjugated with horseradish peroxidase (HRP) is added to all wells and reacts with the biotinylated antibodies. A second washing step is performed. Then the immune complex is visualized by adding Tetramethylbenzidine (TMB) substrate, which gives a blue reaction product. The intensity of this product is proportional to the amount of Thyroglobulin in samples and standards. Sulphuric acid is added to stop the reaction. This produces a yellow endpoint colour. Absorption at 450 and 405 nm is read using an ELISA microwell plate reader.

Specific performance characteristics: 

Intraassay 

Interassay 

Analytic Sensitivity:
The sensitivity was calculated upon the standard curve and expressed as the minimal dose showing a significant difference from standard 0 (mean value + 2 S.D.). This dose is 0.15 ng/ml.

Order information: