The main limitation in systematic calcitonin determination lies in the difficulties in establishing reliable cut-off values, because calcitonin concentration physiologically increases with age and weight, differs according to sex, and may result in false positive cases due to its secretion in neuroendocrine disorders, in lung/pancreas cancer, nephropathy, hypergastrinemia, thyroid autoimmunity. This evidence concerns the gene CALCA and neuroendocrine disorder.