Thyroglobulin (including thyroglobulin antibodies), serum
Clinical Background:
Thyroglobulin (Tg) is a glycoprotein of molecular weight 660,000. It is the principal iodoprotein of the thyroid gland and constitutes the majority of thyroid mass. The circulating levels of Tg ten...
Thyroglobulin (Tg) is a glycoprotein of molecular weight 660,000. It is the principal iodoprotein of the thyroid gland and constitutes the majority of thyroid mass. The circulating levels of Tg tend to increase in a variety of thyroid diseases including toxic and non-toxic goitre, subacute thyroiditis, Graves' disease, and carcinoma. In practice however, measurement of Tg is rarely useful in the diagnosis of disorders of thyroid function. The principal utlility of Tg measurements is in the monitoring of patients with a history of differentiated thyroid cancer who have undergone total thyroidectomy. Detectable Tg post-thyroidectomy suggests the presence of residual thyroid tissue or metastases. Serum Tg is monitored post-treatment as it is a useful marker of recurrance. Thyroglobulin autoantibodies (TgAb) are always measured alongside Tg, as TgAb can cause negative interference in immunometric Tg assays. Undetectable or low Tg concentrations should be intepreted with caution in TgAb positive samples as the measured concentration of Tg may be an under-estimate in such samples.
Test Details
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Discipline:
Biochemistry
Biochemistry
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Specimen Container Adult:
Serum
Serum
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Specimen Container Paediatric:
Serum
Serum
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Minimum Volume Adult:
2 mL blood
2 mL blood
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Minimum Volume Paediatric:
1.5 mL blood
1.5 mL blood
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Sample Stability:
2 days at 4-8°C
2 days at 4-8°C
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Transport Requirements:
Ambient
Ambient
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Interpretation:
Interpretation of Tg and TgAbs:-
Tg <0.1 µg/L and TgAbs <20 kU/L:
A serum Tg <0.1 ug/L while on suppressive levothyroxine therapy, has a negative predictive value for recurrent or persistent thyro...Read MoreInterpretation of Tg and TgAbs:-
Tg <0.1 µg/L and TgAbs <20 kU/L:
A serum Tg <0.1 ug/L while on suppressive levothyroxine therapy, has a negative predictive value for recurrent or persistent thyroid cancer of >98%. In selected patients (eg low risk cases) a serum Tg <0.1 ug/L may obviate the need for assessing serum Tg under TSH stimulation.
Tg ≥0.1 µg/L and TgAbs <20 kU/L:
A serum Tg ≥0.1 ug/L while on suppressive levothyroxine therapy may indicate thyroid remnant, recurrent or persistent disease. Depending on individual circumstances such patients may require further investigation or monitoring for a trend in serum Tg over time before further action.
Tg <0.1 µg/L and TgAbs ≥20 kU/L:
Autoantibodies to Tg (TgAb) may interfere with this Tg and invalidate the result. If serum TgAb is <20 kU/L, interference is unlikely. If serum TgAb is ≥20 kU/L and serum Tg is <0.1 ug/L, persistent/recurrent disease may be masked. In this situation serial serum TgAb measurements may be of value in monitoring the disease.
Tg ≥0.1 µg/L and TgAbs ≥20 kU/L:
If serum Tg is ≥0.1 ug/L and the serum TgAb ≥20 kU/L the result may be an underestimate of the true value. Serial monitoring of both Tg and TgAb is recommended. -
Reference Ranges:
In treated thyroid cancer patients, a thyroglobulin value of greater than 0.1 µg/L may be indicative of recurrent/residual thyroid cancer or persistent thyroid tissue.
In treated thyroid cancer patients, a thyroglobulin value of greater than 0.1 µg/L may be indicative of recurrent/residual thyroid cancer or persistent thyroid tissue.
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Routine Contact Name:
Duty Biochemist
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Routine Telephone:
Freeman: 0191 244 8889
RVI: 0191 282 9719
Freeman: 0191 244 8889
RVI: 0191 282 9719
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Routine Email:
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Specialist Test:
Yes
Yes
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Specialist Contact Name:
Endocrine Lab
Endocrine Lab
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Specialist Telephone:
0191 282 4025
0191 282 4025