Gremlin overexpression is known to cause osteopenia and conditional deletion increases bone mass [65, 66], in agreement with our observation that 0g and ablation upregulate Grem1. Members of the IGF and chemokine families are downregulated by 0g and Pthrp ablation with reversal by PTHrP1-36. The gene discussed is GREM1; the disease is Osteopenia.