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SEARCH FOR MACROCALCITONIN IN PATIENTS BEARING MEDULLARY THYROID CARCINOMA WITHOUT EVIDENCE OF CLINICAL AND IMAGE RECURRENCE

Grant number: 11/19478-2
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): January 01, 2012
Effective date (End): December 31, 2013
Field of knowledge:Health Sciences - Medicine - Medical Clinics
Principal researcher:João Roberto Maciel Martins
Grantee:Thalita Goulart Alves
Home Institution: Escola Paulista de Medicina (EPM). Universidade Federal de São Paulo (UNIFESP). Campus São Paulo. São Paulo , SP, Brazil

Abstract

Medullary thyroid carcinoma (MTC) is a tumor originating from parafollicular cells of the thyroid gland, called C cells, which secrete calcitonin. The MTC is responsible for about 5% of cases of thyroid cancer. Most cases are sporadic, but approximately 30% are associated with a hereditary syndrome known as multiple endocrine neoplasia type 2 (MEN2). MEN2 is an autosomal dominant syndrome in which the predominant manifestation is the MTC. Dominant-activating mutations of the RET tyrosine kinase receptor gene (RET) play a fundamental role in the development of MTC whose more important tumor marker, after total thyroidectomy, is the serum calcitonin. Its determination is crucial for evaluation and long-term management of patients with MTC helping clinicians in detecting cure or local/distant relapse after initial thyroidectomy. However, in the follow-up, some patients maintain calcitonin persistently increased without evidences of relapse or metastasis. This may lead to a pitfall regarding the value of calcitonin and apparent absence of metastatic site suggests possible interferences in the immunometric calcitonin assay. In fact, this artifact has been observed in some cases of macroprolactinemia and macro-TSH in that the increased immunologic levels of those peptides do not reflect a true disease. Accordingly, we propose to search for "macrocalcitonin" in sera from this specific group of patients, once the finding of a negative result could reflect better the pool of calcitonin-producing cells during tumor progression. Moreover, this search will allow a more reliable and specific measure of calcitonin in determining the state of the disease.