GAMT and hyperinsulinemic hypoglycemia, familial, 4: Differently from Cr synthesis defects, where clinical symptoms may be partially reversed by oral Cr supplementation (AGAT deficiency, OMIM 602360) [19,20] or plus a regimen aimed at reducing Guanidino Acetate (GAA) accumulation (GAMT deficiency, OMIM 601240) [2,21,22], Cr supplementation resulted ineffective for CRTR-D [2,3,7,23,24], also when precociously provided [12].