Since the discovery of calcitonin (CT) reports have questioned the physiological role of human CT in regulating calcemia. This peptide is produced out of the CT/CGRP gene splicing along with other factors or hormones, including somatostatin by synonymously called parafollicular cells, C thyrocytes or C cells located in the thyroid glands. The C cells have recently been proven to originate out of the ultimobranchial anlage of the pharyngeal endoderm instead of the neural crest cells as indicated in all textbooks. Both blood and urine CT and procalcitonin (proCT) found in human and other mammals can also be secreted by cells located outside the thyroid glands. Taking account of dietetic calcium intake, CT assists in the homeostasis of bone mineral mass during growth, lactation, and pregnancy, hypo- and hyper gravity along with other paracrine thyroid secretions. Excess CT level in tissue fluids, needle aspirations and, now proCT, can diagnose sepsis, medullary thyroid or other carcinomas; caution to be taken with ectopic CT and gender-difference levels. Salmon CT as diurnal oral delivery seems, if proven not toxic, best suited to continue preventing or treating several defects, especially osteoporosis, orthopedic-related pains, perinatal or acute, fatal hypercalcemia. Contemplating old with recent physiological clinical results, human longitudinal morphologic and molecular data dealing with C cells and their paracrine interactions are few while only animal studies make us know much about CT. Human samples out of biopsies or cadavers should be further endeavored from development to aging to fully correlate normal with extreme or peculiar pathologies.