In addition, the Ret-Hb under B anemias is similar [31,32], whereas Ret-Hb deficiency and high or normal levels in thalassemia have been observed, as the latter coincides with an increase in iron levels as a result of multiple blood transfusions or enhanced iron absorption secondary to ineffective erythropoiesis and hepcidin suppression [33,34]. Here, GSTM1 is linked to hyperinsulinemic hypoglycemia, familial, 4.