090 - Laboratory evaluation of thyroid disease
Autor(s): S. Morbelli, E. Orunesu, G. Pesce, M. Bagnasco
Issue: RIMeL - IJLaM, Vol. 2, N. 1, 2006 (MAF Servizi srl ed.)
Page(s): 90-96
TSH assay is the most accurate parameter for initial evaluation of thyroid disease. In case of abnormal TSH value, further analysis ( fT4 and fT3 assay, anti-thyroid autoantibodies and thyroid scan for differential diagnosis of hyperthyroidism) are required to precise the type of thyroid dysfunction. Concerning fT3 and fT4, clinicians and laboratorists should be aware of the possible source of interference (endogenous antibodies direct against thyroid hormones, heterophilic antibodies, drugs). Anti-thyroid autoantibodies currently assayed are directed against three different antigen: thyreoperoxidasis (TPO), thyroglobulin (TG) and TSH receptor (TR). TPO-Ab are present in up to 95% autoimmune thyroiditis patients and in more than 85% Graves’ disease patients. TG-ab, are less useful in the evaluation of au toimmune thyreopathy but are fundamental in thyroid cancer follow up. In fact, TG-ab can interfere with thyroglobulin assay (used as a marker of thyroid tissue persistence in the follow up of differentiated thyroid cancer). Finally there are two types of TR-ab: inhibiting and stimulating. Stimulating TR-ab are involved in pathogenesis of Graves disease. Regarding thyroid malignancy according to histological types, two different markers are employed. After total thyroid ablation and proved that there is no residual disease, serum thyroglobulin measurement has become the main tool for the early detection of recurrent differentiated thyroid cancer while serum calcitonin is used as marker of medullary thyroid carcinoma. In conclusion it is evident how much laboratory information can support the clinician in the diagnosis and management of thyroid dysfunction. Reciprocal information and collaboration is absolutely relevant for both clinician and laboratorist successful work.