Cite this page: Pernick N. Thyroglobulin. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/chemistrythyroglobulin.html. Accessed March 28th, 2024.
Definition / general
- Prohormone of T3 and T4 synthesized by thyroid follicular cells and cosecreted into serum with T3 and T4
- Serum level is affected by thyroid mass, thyroid injury and TSH receptor stimulation
- Tyrosine residues of thyroglobulin are iodinated with thyroid peroxidase to produce mono- and diiodotyrosyls, which combine to form T3 (mono+di) and T4 (di + di)
- Thyroglobulin releases T3 and T4 into circulation via lysosomal degradation
Laboratory
Indications
Methodology
Monitoring recurrence of well differentiated thyroid carcinoma
Limitations
Reference range
High values
Low levels
- Used primarily to monitor recurrence of well differentiated thyroid cancer after total thyroidectomy or I-131 treatment (Endocr Regul 2006;40:53)
- Also to diagnose thyroid dysgenesis in congenital hypothyroidism (J Med Genet 2005;42:379) or to distinguish subacute thyroiditis (elevated levels) from factitious thyrotoxicosis (undetectable levels despite elevated T3 and T4 levels)
Methodology
- Immunoassay
Monitoring recurrence of well differentiated thyroid carcinoma
- Give patient recombinant human TSH, and measure thyroglobulin 72 hours after last dose
- Rise of serum thyroglobulin above 2 ng/ml (if had remnant ablation and receiving hormone suppressive therapy) correlates with presence of recurrent disease
- Can confirm recurrent disease by whole body iodine scan
- Well differentiated tumors typically have 10x rise in thyroglobuln
- Poorly differentiated tumors may not concentrate iodide, may have blunted response to TSH stimulation
- Can also monitor change of thyroglobulin level when receiving T4 treatment post-thyroidectomy (J Clin Endocrinol Metab 2005;90:5047)
Limitations
- 20% with thyroid cancer have antithyroglobulin antibodies which interfere with assay (falsely lower serum concentration by binding to thyroglobulin and making it "invisible" to the assay)
- Should determine presence of antibodies when measure thyroglobulin level for tumor monitoring
- If antibodies are present, PCR may be useful to measure thyroglobulin
- Also interference by heterophile antibodies (J Clin Endocrinol Metab 2003;88:3069)
Reference range
- < 30 ng/ml (45 pmol/L)
High values
- Graves disease, thyroiditis, nodular goiter, well differentiated thyroid carcinoma
Low levels
- Factitious thyrotoxicosis (surreptitious use of thyroid hormone-levels are undetectable although T3 or T4 are elevated)