Potency and Tolerance of Calcitonin Stimulation with High Dose ...

Introduction
Human calcitonin (hCT) is a tumor marker essential to the diagnosis and follow-up of
medullary thyroid cancer (MTC ) (1-4). Current European consensus recommends hCT
measurement when initially evaluating thyroid nodules (5). If hCT is mildly elevated,
European centers commonly perform a confirmatory test with intravenous pentagastrin
stimulation (3, 6-8). A less popular alternative stimulation test uses a short intravenous
calcium infusion (3, 6). Stimulation testing also may aid early risk stratification in patients
with MTC (4).
For reasons including the unavailability of pentagastrin in the US, the American
Thyroid Association has not recommended routine hCT measurement (9). However, a recent
U.S. cost-effectiveness study (10), though not without flaws, provides data favoring such
testing .
Key to employing stimulated hCT measurement clinically are the reliability and
relevance to everyday practice of healthy adult reference values. Most published reference
values for stimulation tests were obtained in small series not rigorously screened for thyroid
abnormality (2, 6, 7, 11). Calcium stimulation was investigated in only a few studies (12)
using disparate regimens, e.g., 10% calcium gluconate dosages of 2.0-2.5 mg/kg body weight,
injection over 30 sec-5 min (3, 13-15).
Indeed, hCT reference ranges generally were obtained with competitive
radioimmunoassays and do not apply to automated non-competitive chemiluminescent
immunometric assays.
Differences in hCT measurement are evident even within the radioimmunoassay
class, emphasizing the need to re-evaluate reference ranges and cut-off values for each assay
individually (16).
We therefore conducted this study to define the normal ranges on a commonly used
chemiluminescent immunometric assay of serum hCT values in healthy adults before and
after pentagastrin or high-dose calcium stimulation,. We also sought to assess these
secretagogues’ tolerability in such subjects..
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