Gamma-glutamylornithine excretion in patients with hyperornithinemia

Gamma-glutamylornithine has been identified in urine from patients with the HHH syndrome (hyperornithinemia, hyperammonemia and homocitrullinuria) and with gyrate atrophy associated with hyperornithinemia. The amount of gamma-glutamylornithine excreted was 10-15 times higher than that excreted in normal subjects. The level of excretion was comparable in the HHH syndrome subjects and the gyrate atrophy subjects despite the fact that the gyrate atrophy subjects excreted more ornithine. A 100 mg/kg oral challenge of ornithine increased the excretion of gamma-glutamylornithine by a factor of three. This increased excretion of gamma-glutamylornithine was observed in hyperornithinemia patients with different etiologies and is therefore presumably due to the hyperornithinemic state, per se, independent of the underlying defect.