Polymorphisms of a number of genes differentially expressed in our rat bone array have been associated with susceptibility to human osteoporosis [29]–[31]: Opg (skull∶limb, fold increase 3.1), Vdr (4.8), Pthr1 (2.9), Calcr (4.6), Lrp5 (2.2), and Ctsk (2.7), Alox12 (0.2), Table 1. The gene discussed is PTH1R; the disease is osteoporosis.