Calcitonin is widely used for the acute treatment of metabolic bone disorders, such as osteoporosis (Muñoz-Torres et al., 2004) and Paget's disease (Langston and Ralston, 2004) – though, paradoxically, humans with varying levels of endogenous calcitonin [e.g. persons that have undergone thyroidectomy or with C-cell-derived medullary thyroid carcinoma (MTC)] exhibit no differences in bone mineral density (Hurley et al., 1987; Wuster et al., 1992). Here, CALCA is linked to medullary thyroid gland carcinoma.