IS ROUTINE
MEASUREMENT OF CALCITONIN JUSTIFIED IN PATIENTS WITH THYROID NODULES?
Calcitonin
is a hormone produced by the parafollicular cells (or C-cells) of the thyroid
gland. Calcitonin is involved in the regulation of calcium and phosphate levels
in the blood, opposing the actions of parathyroid hormone. Increased production
and therefore increased levels of calcitonin is occurred in patients with
C-cell hyperplasia (CCH) and medullary thyroid cancer (MTC). CCH is considered
as a preneoplastic pathological entity (prior to the development of MTC),
although it can occur as a local reactive process (for example in the presence
of a localized papillary thyroid cancer). Serum calcitonin measurement in
patients with thyroid nodules could detect CCH and mainly MTC (as a
‘neoplasmatic marker’) theoretically at an earlier stage thereby improving
overall survival. However, in practice, many uncertainties and unanswered
questions still exist. In many studies, serum calcitonin measurement was used
in association with pentagastrin stimulation, a test which is not widely
available with some unresolved issues such as sensitivity, specificity, details
of its performance, cut-offs value using calcium stimulation etc. Moreover,
detection of CCH and microMTC, may complicate the interpretation of the value
of routine measurement of calcitonin, since these two entities have
questionable biological significance.
Serum
calcitonin measurement should be strongly considered when an increased
calcitonin level could modify the surgical strategy (for example, when a less
than total thyroidectomy is considered) or when cytology (FNA) results indicate
suspicious lesion not consistent with papillary thyroid cancer. Serum
calcitonin levels > 50 – 100 pg/mL typically indicates the presence of MTC.
Calcitonin
could also be measured in the FNA-washout to document preoperatively the
diagnosis of MTC, especially in patients with marginal increase in basal serum
calcitonin levels (20 -100 pg/mL).
In
conclusion, the role of routine serum calcitonin measurement in patients with
thyroid nodules remains controversial. Calcitonin should be measured in the
serum or in the FNA-washout of selected patients with thyroid nodules.
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