Given that plasma Cr is being filtered and lost in the urine due to CrT deficiency, we could expect that Cr levels in plasma were diminished and those of GAA, the precursor of Cr, were increased in an attempt to compensate Cr levels by AGAT feedback loop of up-regulation due to Cr deficiency (for this mechanism in periphery2,35,36 or for CNS37). Here, SLC6A8 is linked to hyperinsulinemic hypoglycemia, familial, 4.