Mice lacking the Esp gene, which encoded osteotesticular protein tyrosine phosphatase (OST-PTP), a receptor-like protein that inhibited the bioactivity of osteocalcin, exhibited hypoglycemia and were protected from glucose intolerance due to increases in pancreatic β-cell proliferation, insulin secretion and insulin sensitivity (10). The gene discussed is BGLAP; the disease is Hypoglycemia.