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Thyroglobulin (Tg) is a large (660kDa molecular weight) glycoprotein that is synthesized in the thyrocyte and secreted into the thyroid colloid. It is the framework for thyroid hormone synthesis and has an important role in intracellular regulation (31-33). Healthy euthyroid glands release Tg into the circulation in small amounts (34-36). Upon hyperstimulation of the thyroid by TSH or thyroid stimulating antibodies, production and release of Tg is elevated. Tg is a sensitive indicator of both low and excess iodine intake, following a U-shaped curve in response to iodine excretion (7), as shown in school-age children (7, 19), pregnant women (5, 6)and infants (4). Research has demonstrated the utility of Tg to confirm improved thyroid function after iodine repletion (19, 21, 37). Due to a high day-to-day variability, however, the utility of Tg as an individual biomarker of iodine status is uncertain (38).


There are numerous different ways to measure Tg, including immunoassay (including ELISA), radioimmunoassay, dedicated kits, and by mass spectrometry (6, 18, 39).

Note: Blood, as whole blood, plasma, serum or on dried blood spots, is a potential biohazard, and safety precautions should be employed at all times whilst handling or manipulating samples.

LC-MS: For an example method measuring Tg by liquid chromatography-tandem mass spectrometry (LC-MS), see reference (39), available here.

Serum ELISA: Click the following link to download the Serum-ELISA method protocol: Serum Tg ELISA SOP
Kindly provided by the Human Nutrition Laboratory, ETH Zurich, Zurich, Switzerland.

An ELISA technique has been developed using dried blood spots (DBS) (18), which facilitates the collection, processing, storage and transport of blood samples, and is a field-friendly method of Tg assessment, suitable for use in LMIC settings. This method has validated reference ranges for iodine sufficiency in school-age children and pregnant women (6, 7, 19, 21)(see table on page 3).

Click the following link to download the DBS-ELISA method protocol: DBSTg ELISA SOP
Kindly provided by the Human Nutrition Laboratory, ETH Zurich, Zurich, Switzerland.

Notes on the DBS method: Antibodies are ordered from HyTest (see protocol). Orders must be made by email.
When ordering the Anti-Tg HRP-cojugated antibody (antibody 2), ensure to quote “in agreement with ETH Zurich”, since Hytest only manufacture this antibody for laboratories wishing to undertake this assay: “2TG12ccC 5E6cc Anti-Thyroglobulin HRP-conjugated, in agreement with ETH Zurich”.

Quality control

For all methods, in-house quality controls should be prepared from volunteers with low and high Tg concentrations, respectively.

Venous blood samples can be drawn from volunteers and spotted onto filter paper cards using a pipette set to 50 μL. Note: blood should be drawn into the appropriate tube: blood tubes with EDTA as an anticoagulant should not be used to handle blood for Tg analysis, since the EDTA can interfere with sample assessment (40).

Standards should be produced using washed red blood cells and the Biorad Liquicheck Tumor Marker Controls # 547, 548 and 549. Haematocrit and blood spot volume should be carefully controlled when these reference materials are produced. For an example method, please contact OpeN-Global.

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