SLC6A8 and hyperinsulinemic hypoglycemia, familial, 4: However, the characteristic biochemical features of each CCDD is unique: elevated guanidinoacetate in body fluids in GAMT deficiency, low or low normal urine guanidinoacetate and low plasma guanidinoacetate in AGAT deficiency and elevated urine creatine in CRTR deficiency in males.