Abstract
Calcitonin (Ct) is a tumour marker essential for the diagnosis and follow-up of medullary thyroid cancer (MTC). Accurate and consistent measurements of serum Ct are of critical importance. Ct measurements by different methods can differ, leading to difficulties in the interpretation of results. Second generation assays for Ct have been developed and are now available in clinical laboratories. However, the lack of standardization for Ct assays remains a common problem with Ct assays. The reference interval and reliability should be carefully defined.The role of stimulated Ct for the diagnosis and follow-up of MTC should also be pointed out as the pentagastrin test is no more available in all countries. However, the stimulated test remains very useful to exclude MTC if the basal Ct serum level is in the grey zone (15-20 ng/L), after surgery to confirm the complete cure. A residual response after surgery could indicate a need for aggressive surgery or - in case of metastatic disease - could suggest the prognosis.High-dose Ca test (2.5mg/kg) seems to be a reliable and effective test for the diagnosis and follow-up of MTC. It seems more potent than pentagastrin with fewer side effects. The threshold able to discriminate healthy subjects from C-cell hyperplasia (CCH) cases for the stimulated Ct concentration is 184 ng/L for women and 1620 ng/L for men.As stimulated Ca test will eventually replace the pentagastrin test, there is a need to confirm or to modify the threshold identified for each assay individually.
Highlights
Medullary thyroid carcinoma (MTC) originates from thyroid C cells, which secrete calcitonin (Ct).Routine measurement of Ct in patients with nodular goitre allows for the preoperative diagnosis of unsuspected medullary thyroid cancer (MTC), often at a very precocious stadium.Ct is a 32 amino- acid- polypeptide, in which the disulphide bridges are essential for biological activity
Verga et al [11] showed that a peak above 50ng/L indicated a risk of C-cell hyperplasia (CCH) and MTC, while Scheuba et al [12] found that the probability of having an MTC was 100% if the peak value was higher than 560 ng/L; Elisei et al [13] determined the lowest peak of Ct for MTC to be 118 ng/L
Provided these references ranges are clearly assessed, the indications and usefulness of the high-dose calcium stimulation test should be very similar to the “old “ pentagastrin test. Evaluation of both basal and stimulated Ct may be useful in the diagnosis and follow-up of MTC
Summary
Medullary thyroid carcinoma (MTC) originates from thyroid C cells, which secrete calcitonin (Ct). The question arises whether the decisionmaking can be reliably based on a single basal Ct measurement for diagnosis in patients with a genetic susceptibility to develop MTC (i.e., activated RET oncogenecarriers) or for the follow-up after surgery for a known MTC This strategy was recently recommended by the American thyroid association as the pentagastrin is unavailable in many countries [8]. The stimulation test remained very useful to exclude an MTC in an unaffected individual when basal Ct was in the grey zone (15-50 ng/L) as observed in autoimmune thyroiditis with CCH or in neuroendocrine tumours Another indication for the stimulation test was to detect residual disease or recurrence after surgery for MTC in patients with low basal Ct levels. Blood samples are obtained at baseline, and two and five minutes after pentagastrin injection
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