TG

REF 24-08

ELISA kit ("sandwich" type) for the quantitative determination of thyroglobulin in human serum. 

Thyroglubulin (TG) is the main protein produced by thyroid gland. It is the precursor and a deposit form of thyroid hormones thyroxin (T4) and triiodothyronine (T3).TG is an iodinated glycoprotein with molecular weight of 660 KDa consisting of two subunits.

TG concentration in serum depends on thyroid gland weight, its functional status and inflammation degree. In healthy people TG concentration varies from 2 to 50 ng/ml and may increase ca. twice during pregnancy. After surgical operation or treatment with radioactive iodine TG concentration remains increased for several weeks. In population suffering from environmental iodine deficiency average blood TG concentration  is increased. Since 1994 TG has been regarded by WHO as one of indicators of endemic goiter.

Serum TG measurement is performed mostly for monitoring the  thyroid carcinoma patients. TG concentration dynamics serves a marker for evaluation of treatment efficiency, revealing of possible recurrence and metastases in patients after thyrectomia. This parameter is not used for primary diagnostics of thyroid cancer.

TG concentration in serum may be useful for exact diagnostics at congenital hypothyrosis. Increased TG concentration permits to differentiate subacute thyroiditis from pharmacological thyrotoxicosis (when TG level remains stable). In patients with Grave’s disease increase in TG concentration is a preliminary sign of recurrency after canceling of suppressive therapy.

TG measurement may be affected by presence of anti-TG autoantibodies in the serum sample. In this case the results may be false-negative. To obtain the reliable results it is recommended always to combine TG and anti-TG autoantibodies determination.

Serial TG determinations for patient monitoring should be always done by the same method. The physician should be always informed not only of the results of TG determination but also of the type of assay used. When the type of diagnostic kit is changed, the laboratory must perform the appropriate clinical evaluation and compare the range of the results obtained with two types of kits.