This is a test for patients with symptoms suggestive of disorders in creatine metabolism.
The creatine/creatine-phosphate system plays an important role in the storage and transmission of phosphate-bound energy. Creatine is synthesised in the liver and pancreas from arginine and glycine with guanidinoacetate methyltransferase (GAMT) and arginine:glycine amidotransferase (AGAT) as enzymes. Intracellular creatine and creatine-phosphate are non-enzymatically cycled to creatinine which is mainly excreted in urine and daily excretion is directly proportional to total body creatine.
GAMT deficiency has a wide clinical phenotype ranging from predominance of extrapyramidal encephalopathy and intractable epilepsy to moderate mental retardation. Patients have systemic depletion of creatine and creatine-phosphate due to impairment of de novo creatine biosynthesis but increased guanidinoacetate excretion.
Patients with the very rare AGAT deficiency have decreased excretion of creatine, creatinine and guanidinoacetate.
Creatine transporter deficiency shows normal guanidinoacetate and creatinine concentration with increased creatine excretion.
Please request a random urine for screening of these disorders. A plasma sample is only required to confirm urine findings.