CASR and airway hyperresponsiveness: The first hint of a possible involvement of the CaSR in the pathophysiology of asthma came from the observation that in inflamed lungs of asthmatics there is an accumulation of known CaSR agonists, i.e., eosinophil cationic protein, spermine, spermidine, and putrescine, that seem to directly contribute to airway hyperresponsiveness (AHR) and lung inflammation (Kurosawa et al., 1992; Coyle et al., 1993; Gibson et al., 1998; Koller et al., 1999; Homma et al., 2005; Pégorier et al., 2006; North et al., 2013).