LDLR and hyperinsulinemic hypoglycemia, familial, 4: To obtain leptin deficiency (ob/ob) on a background of LDLR deficiency, LDLR−/− and ob/+ mice were crossed, and the F1 progeny of this mating (LDLR−/+;ob/+) were then crossed to obtain mice that had either zero, one, or both normal LDLR alleles and were leptin-deficient (LDLR−/−;ob/ob, LDLR+/−;ob/ob, and LDLR+/+;ob/ob, respectively) as well as control LDLR−/−, LDLR+/−, and wild-type mice.