These varying effects of PTH/PTHrP activity are seen in two skeletal dysplasias that result from mutations in PTH1R; Jansen Metaphyseal Chondrodysplasia (JMC) (Cohen, 2002), an autosomal dominant disease that results from constitutive action of PTH1R (Schipani et al., 1995) and Blomstrand Chondrodysplasia (BOCD) (Loshkajian et al., 1997), an autosomal recessive disorder caused by loss-of-function mutations in PTH1R (Jobert et al., 1998). This evidence concerns the gene PTH1R and autosomal dominant disease.