From the Guidelines
No, procalcitonin is not the same as calcitonin, as procalcitonin is a precursor molecule to calcitonin, consisting of 116 amino acids, while calcitonin is a smaller 32-amino acid hormone. According to the most recent study 1, procalcitonin is produced in various tissues throughout the body in response to bacterial endotoxins and inflammatory cytokines, causing blood levels to rise significantly, making it a valuable biomarker for bacterial infections and sepsis. In contrast, calcitonin functions primarily as a hormone that regulates calcium metabolism by inhibiting osteoclast activity in bones, thereby reducing serum calcium levels.
Key differences between procalcitonin and calcitonin
- Procalcitonin is a precursor molecule to calcitonin, consisting of 116 amino acids, while calcitonin is a smaller 32-amino acid hormone
- Procalcitonin is produced in various tissues throughout the body in response to bacterial endotoxins and inflammatory cytokines, while calcitonin is primarily produced in the thyroid C-cells
- Procalcitonin levels rise significantly during bacterial infections, making it a valuable biomarker for bacterial infections and sepsis, while calcitonin functions primarily as a hormone that regulates calcium metabolism
Clinical applications of procalcitonin
- Procalcitonin can be used as a biomarker for bacterial infections and sepsis, with levels typically increasing within 2-4 hours of infection onset
- Procalcitonin-guided antibiotic stewardship can help reduce antibiotic use in stable, low-risk patients with respiratory infections, as demonstrated by several RCTs 1
- Procalcitonin levels can guide antibiotic discontinuation in ICU patients with suspected sepsis, with levels of less than 0.5 µg/L or levels that decrease by greater than or equal to 80% from peak levels indicating potential discontinuation 1
From the Research
Definition and Relationship
- Procalcitonin is a propeptide of calcitonin, indicating that it is related to calcitonin but not the same molecule 2.
- Procalcitonin is a polypeptide consisting of 116 amino acids, whereas calcitonin is the hormone produced by the C-cells of the thyroid gland 2.
- The synthesis of procalcitonin is upregulated in bacterial infection and downregulated by viral infection, making it a useful marker for differentiating between types of infections 3.
Clinical Use
- Procalcitonin is used as a marker for detecting bacterial, fungal, and protozoal infections, and can be used to guide antibiotic stewardship in critical patients 2, 4.
- The value of procalcitonin depends on the specific clinical situation and pretest probability of disease, and its use should be guided by laboratory testing and clinical expertise 3, 4.
- Procalcitonin can be used to differentiate between infectious and non-infectious forms of systemic inflammatory response syndrome, although its power in doing so is limited 4.
Comparison to Calcitonin
- Procalcitonin and calcitonin are related but distinct molecules, with procalcitonin being the precursor to calcitonin 2, 3.
- While calcitonin is produced by the C-cells of the thyroid gland, procalcitonin can be produced by extrathyroidal tissues during severe systemic infections 2.
- The clinical use of procalcitonin is focused on its role as a biomarker for infection and sepsis, whereas calcitonin is primarily involved in calcium homeostasis 2, 3.