Procalcitonin: Mysterious Protein in Sepsis Misa Nakamura

Septic shock is a leading cause of mortality in intensive care units, but can be difficult to distinguish from non-infectious conditions in critically ill patients admitted with clinical signs of acute inflammation. Procalcitonin (ProCT), the precursor of the hormone calcitonin, is composed of 116 amino acids and has a molecular weight of 13 kDa. In contrast to many pro-inflammatory cytokines (e.g., tumor necrosis factor alpha and interleukin-1 beta) that rise and decline in the early course of sepsis, serum ProCT is increased in patients with sepsis and those with systemic inflammation, correlates with the mortality and severity of illness, and remains elevated over a relatively long period of time. Hence, ProCT appears as an important marker of sepsis. In response to microbial infections, ProCT may play a causative role in the tissue damage because treatment with ProCT-neutralizing antiserum increases animal survival in the animal models of sepsis. Conversely, an anti-inflammatory effect of the ProCT has also been reported in humans stimulated with endotoxin. Awareness of the clinical effects of ProCT has led to increased interest in understanding its regulation and biological role. In this review, we first describe the biological characteristics of ProCT and then discuss its impact on the clinical medicine