CALCA and infection: Being produced by an unknown source (it may be produce in the liver or by macrophages), it is secreted into the blood circulation during infection without increasing calcitonin.14 PCT is detectable in the plasma as early as 2 h after the exposure to the bacterial products; its level rises for 6 to 8 h, reaches a plateau after 12 h, and then decreases to a normal level after 2 to 3 days.15