Baseline MR spectroscopy showed a decreased creatine peak level of 2.42 ppm in both the parietal and right temporal lobes (Fig. 6c), and a urine analysis revealed a significant elevation in the creatine/creatinine ratio (43.9, ref; 0.017–0.720) corresponding to a creatine transporter deficiency. Here, SLC6A8 is linked to hyperinsulinemic hypoglycemia, familial, 4.