http://www.creativebiomart.net/description_382774_12.htm

Procalcitonin is a peptide precursor of the hormone calcitonin. It is composed of 116 amino acids and mainly produced by the C cells of the thyroid and certain endocrine cells of the lung. Calcitonin participates in calcium (Ca2+) and phosphorus metabolism. In many ways, calcitonin counteracts parathyroid hormone (PTH). Calcitonin can lower blood Ca2+ levels. It also inhibits phosphate reabsorption by the kidney tubules. Procalcitonin correlates with bacterial load and severity of infection. Procalcitonin thus has prognostic implications and is taken as a promising candidate marker for diagnosis and for antibiotic stewardship in patients with systemic infections