Thyroglobulin (TG) | Laboratory research

Thyroglobulin (TG) Is a glycoprotein that serves the synthesis of thyroid hormones. It is the most important protein component of the thyroid gland, which is synthesized in large quantities by thyroid cells and accumulates in the follicular lumen.

Each thyroglobulin (TG) macromolecule contains 25 tyrosine (amino acid) molecules - the major substrate for thyroid hormone synthesis. The gradual conversion of thyroglobulin (TG) results in the biosynthesis of thyroid hormones, and in the final stage, by stimulating TSH, thyroxine (T4) and triiodothyronine (T3) are converted into blood.

Small amounts of thyroglobulin (TG) are released into the thyroid gland during thyroid cell synthesis (TG) synthesis and during thyroid follicle transport. On the other hand, when the follicular wall is damaged, a larger amount of thyroglobulin (TG) enters the bloodstream; Therefore Thyroglobulin (TG) is a marker of morphological integrity of the thyroid gland.

An increase in thyroglobulin (TG) is caused by three types of thyroid disease:

• Thyroid goiter with hyperfunction;
• Inflammation or traumatic injury to the thyroid gland;
• Differentiated thyroid cancer.

When should we take a thyroglobulin test?

The test determines the amount of thyroglobulin (TG) in the blood and it is often used as Tumor marker, To monitor the following conditions:

• Differentiated cancer of the thyroid gland Monitoring of patients with thyroidectomy and treatment with radioactive iodine.
  Thyroglobulin (TG) will not be detected in patients with thyroid cancer who do not have any remaining thyroid tissue damaged after surgery or radiation. Thus, thyroglobulin (TG) is an informative tumor marker for the presence of residual (residual) thyroid papillary follicular carcinoma after surgical resection and / or irradiation.
  If we have thyroglobulin values ​​-> 3 μg / L on the face during thyroxine-suppressing therapy, it is an indicator of tumor recurrence and a whole body scintigraphy with iodine 131 is recommended.
• Destructive thyroiditis;
• Differential diagnostics between subacute thyroiditis and artificial thyrotoxicosis (In artificial thyrotoxicosis, thyroglobulin levels are very low or not detected at all.)
• Congenital hypothyroidism, Differentiate between congenital absence of the thyroid gland and hypoplasia of the thyroid gland or other pathological conditionsEba.
• Studies related to the assessment of iodine deficiency in the population.

We must remember that Not all malignant tumors of the thyroid gland produce thyroglobulin. However, more common types of cancer have elevated thyroglobulin levels.

A thyroglobulin test should be performed in conjunction with a thyroid hormone (FT3, FT4) and thyroid-stimulating hormone (TSH) test before treatment to determine if the tumor is thyroglobulin-producing.

The test is performed during the following symptoms of hormonal imbalance:

• Sudden weight loss despite preserved appetite;
• Unexplained weight gain;
• Itchy skin;
• Sudden weakening of vision;
• Irritation;
• Increased growth of facial and body hair;
• Decreased libido;
• Sudden mood swings;
• Sleep disorders.

How to prepare for the test?

The test is preferably taken on an empty stomach, in the morning (until about 11 o'clock). The test should be performed before the start of scanning procedures and thyroid biopsy, or no earlier than 2 weeks thereafter, and not earlier than 131 weeks after the end of thyroidectomy or iodine 6 therapy.

Possible interpretation of the results

An increase in thyroglobulin in patients with thyroid cancer allows it to be used as a tumor marker.

Thyroglobulin is not detected or is very low after surgical removal of the thyroid gland or radioisotope treatment.

If high thyroglobulin levels are still observed after treatment, it probably means that there are residual tissues of the thyroid gland or tumor that require your attention and monitoring.

If high thyroglobulin levels are detected within a few weeks or months of surgery, this is likely to indicate a recurrence or spread of the tumor.

Thyroglobulin (TG) concentration increases:

• Thyroid tumors;
• Subacute thyroiditis;
• Thyroid adenoma;
• Hyperthyroidism;
• Thyroid cancer metastases;
• Endemic goiter;
• Iodine deficiency;
• Graves' disease;
• Post-treatment condition with radioactive iodine

Thyroglobulin (TG) concentration decreases:

• Thyroid hyperfunction caused by excessive intake of thyroid hormones.