Leucine loading test

It has been suggested that heterozygotes for the disease may excrete increased concentrations of isovalerylglycine in their urine after a leucine load test (Guibaud et al., 1973) when compared to controls, in whom no excretion of this compound was observed. Serum leucine and isovaleric acid concentrations were not affected in similar tests carried out by others (Levy etai, 1973), but such a test with isovalerylglycine monitoring may be useful to demonstrate heterozygosity. 

Measurement of blood ketones during 3 h after the load. The test is only applicable to patients with HMGS deficiency, who will produce ketone bodies after leucine in contrast to LCT or MCT loading tests [21]. 

Her very low-protein diet was continued, but in order to ensure an adequate supply of essential amino acids for growth she was fed a mixture of the ketoacids of threonine, methionine, leucine, isoleucine and valine. After each feed she again became abnormally drowsy and markedly ketotic, with significant acidosis. Her plasma ammonium ion concentration was within the normal range, and a glucose tolerance test was normal, with a normal increase in insulin secretion after glucose load. 

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