Influence of muscle wasting on oral glucose tolerance testing.

1. The effect of muscle wasting on glucose tolerance was studied. Oral glucose tolerance testing was performed in three groups of wasted patients: myotonic dystrophy (11); amyotrophic lateral sclerosis (10); other lower motor neuron disease (four). Normal subjects (11) and non-wasted neurological disease (five) controls were studied for comparison. An average decrease of 29-36% in lean body mass was present in the wasted individuals. 2. A slightly higher plasma glucose occurred at 120 min after glucose ingestion in wasted compared with non-wasted individuals (119.2 +/- 5 vs. 99.9 +/- 4 mg/100 ml, P less than 0.05). 3. Normal insulin release was seen in all patient groups except those with myotonic dystrophy, who displayed marked hyperinsulinaemia from 30 to 240 min after glucose. This excessive insulin output was not due to a greater absolute decrease in lean body mass in the myotonic dystrophy patients than in the other wasted subjects. No significant correlation between the cumulative insulin release or peak insulin values and the absolute or height adjusted lean body mass was noted within any of the wasted or non-wasted groups. 4. In contrast to the findings of many studies, only clinically insignificant glucose intolerance was detected in ambulatory wasted patients and only patients with myotonic dystrophy had abnormal insulin release. Muscle loss appeared to exert only a slight influence on glucose regulation in these wasted patients and no typical effect of muscular atrophy on pancreatic insulin release was noted.