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

versa. Similar findings in healthy subjects were noted by Gharib et al. (14), who used a
different calcium infusion regimen (2mg/kg over 5 min) than ours and injected pentagastrin as
a bolus. However, in that study, pentagastrin provided more potent stimulation than did
calcium in a 12-person subgroup of thyroidectomized MTC patients (14). Additionally,
Costante et al. reported that a 30-second infusion of calcium gluconate, 2.5 mg/kg, was
equally effective as pentagastrin in identifying patients with C-cell hyperplasia or MTC (3).
Therefore the impact of the calcium regimen and the comparative efficacy of the two agents
in clinical practice remain unclear. Additional trials investigating hCT levels in patients with
thyroid abnormalities, such as multinodular goiter and autoimmune thyroiditis, and MTC
patients are necessary to resolve these issues and define appropriate cut-off values for disease.
In line with previous observations, virtually all subjects reported greater transient
discomfort of varying intensity after pentagastrin than after calcium (3, 17, 18).
This study had several limitations. Since all subjects underwent pentagastrin
stimulation before calcium stimulation, a sequencing effect was possible; however, the
months-long wash-out between stimulation tests renders this unlikely. The wash-out’s length,
however, may have contributed to the loss to follow-up of an appreciable portion (16%) of
subjects, which may have introduced bias into the comparison of the stimulation agents.
Additionally, the study included no elderly subjects or MTC patients.
Conclusions
In healthy young to middle-aged adults, calcium seems to be a more potent and
better-tolerated hCT stimulator than is pentagastrin. The reference ranges for basal and
stimulated hCT for healthy adults established via automated chemiluminescent assay were
lower than those reported for other assays. Gender-based cut-offs may be unnecessary for
unstimulated, but necessary for stimulated hCT testing.
Acknowledgements
We thank Petra Völcker, Werner Kühnel and Robert Marlowe for their assistance.
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