Procalcitonin (PCT) is a precursor of the hormone calcitonin. Under physiological conditions, calcitonin is produced and secreted by the C cells of the thyroid as a result of pro calcitonin proteolysis; therefore, procalcitonin is almost absent or present at very low levels, on the order of picograms. However, under conditions associated with systemic inflammation, procalcitonin is produced and secreted almost ubiquitously. In summary, therefore, calcitonin is produced exclusively by C cells of the thyroid in response to hormonal stimuli. In contrast, several cell types and many organs can produce PCT in response to proinflammatory stimuli. Bacterial endotoxins and proinflammatory cytokines are the primary stimuli for PCT production. Viral infections and neoplastic and autoimmune diseases generally do not stimulate PCT production, except occasionally and at low concentrations. In addition, chronic non-bacterial inflammation and allergic reactions do not increase PCT levels.

The amount of PCT released and, therefore, the increase in circulation is related to the extent of the inflammatory reaction; very high values are generally found in severe acute bacterial infections and sepsis. Experimental studies have shown that PCT values increase with the severity of sepsis, reaching very high values in subjects with septic shock and being associated with increased mortality.

Localized bacterial infections not associated with symptoms of systemic inflammation (e.g., fever) or septic reactions result in low PCT values.

Table 1 shows the reference values of the PCT.

Table1. Interpretation of circulating levels of procalcitonin (PCT)

PCT is very sensitive and specific for bacterial infections. Experimental studies have shown that PCT levels increase rapidly (approximately 3 hours) following endotoxin administration, with a peak around 12 hours. At the end of the acute inflammatory reaction, PCT concentration decreases rapidly because it has a short half-life (20–24 hours). In clinical practice, PCT aids in guiding and monitoring antibiotic therapy; in this context, it is important not so much the absolute value but rather its variations over time.

PCT is a very stable protein in vivo and in vitro: in circulation, it is not degraded to the active hormone calcitonin.

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مواضيع ذات صلة

Erythrocyte Sedimentation Rate

C-Reactive Protein

plasminogen (Fibrinolysin)

placental growth factor (PGF)

PI-linked antigen (Phosphatidylinositol antigen)

Pre-implantation Diagnosis

Pepsinogen

Parkinson disease testing

Papanicolaou smear (Pap smear, Pap test, Cytologic test for cancer, Liquid-based cervical cytology [LBCC], ThinPrep)

Carrier Diagnosis

oximetry (Pulse oximetry, Oxygen saturation)

5′-nucleotidase