GSTM1 and hyperinsulinemic hypoglycemia, familial, 4: The nadir median Hb concentration was lower for patients with normal ITPase activity compared to patients with ITPase deficiency, respectively 6.6 mmol/L (IQR 5.8–7.2) and 7.2 mmol/L (IQR 6.6–8.1, p<0.001).