Journal of investigative medicine : the official publication of the American Federation for Clinical Research
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The systemic inflammatory response syndrome (SIRS) is a marked, generalized response to a variety of injuries, if infection is implicated, the term "sepsis" is used. Systemic inflammatory response syndrome/sepsis, which is initiated by proinflammatory cytokines, has been found to be associated with increased serum levels of the prohormone of calcitonin, procalcitonin (ProCT) and its aminoterminus peptide (nProCT). The serum levels of ProCT and nProCT are very useful markers for SIRS/sepsis, and may be used to follow the course, the response to therapy, and/or the prognosis. We studied the serum levels and distribution of ProCT and its component peptides in normal persons for comparison with similar immunochemical and separatory studies in patients with neuroendocrine cancer and with SIRS/sepsis of various etiologies. ⋯ These studies indicate that ProCT and its component peptides circulate in normal persons. The serum of patients with SIRS/sepsis contains greatly increased levels of ProCT, nProCT and often, CT:CCP-I. However, in this condition, post-translational processing is incomplete, resulting in mature CT levels that are normal or minimally elevated. In contrast, patients with neuroendocrine cancer have considerably high mature CT levels. Interestingly, although serum CGRP levels often are high in neuroendocrine cancer, they are low in SIRS/sepsis. The marked hyperprocalcitonemia of SIRS/sepsis is probably a consequence of the pro-inflammatory cytokine cascade, and appears to be secreted in a constitutive fashion; the cell(s) of origin of this remarkable hypersecretion is unknown. There is a very marked positive correlation between serum levels of ProCT and nProCT, and the lower level of sensitivity for nProCT may make its measurement a more useful marker for early or mild SIRS/sepsis.