Procalcitonin (PCT) is a small protein (~13 kDa) that is synthesized by the C-cells of the thyroid glands. It is considered to be the main marker of disorders that are accompanied by systemic inflammation and sepsis.
PCT is encoded by the CALC-1 gene and it is the precursor of the calcitonin hormone. It is produced from a 141 amino acid long pre-procalcitonin. After removal of the signal peptide (amino acids 1-25), the 116 amino acid long PCT undergoes successive cleavages to form three molecules: N-terminal fragment (N-terminal PCT, 57 amino acid residues (a.a.r.)), calcitonin (32 a.a.r.) and katacalcin (21 a.a.r.).
PCT belongs to a family of related proteins (the CAPA peptides family), which also includes calcitonin, the calcitonin gene-related peptides I and II, amylin and adrenomodulin.