<prompt> Procalcitonin is used as a marker for?SepsisMedullary carcinoma of thyroidVitamin D resistant ricketsparathyroid adenoma  <response>: Answer is option 1, sepsis Prompt diagnosis and treatment with appropriate antimicrobial chemotherapy is of paramount impoance to reduce morbidity and moality associated with sepsis. Inflammatory markers currently in use, such as C-reactive protein CRP do not reliably differentiate between the systemic inflammatory response and sepsis. Procalcitonin PCT, a precursor of calcitonin, is a 116 amino acid protein that has been proposed as a marker of disease severity in conditions such as septicaemia, meningitis, pneumonia, urinary tract infection UTI and fungal and parasitic infection. Ref : 