Plasma insulin and C-peptide in normal and glucose intolerant males: the role of hepatic insulin uptake.

Plasma immunoreactive insulin and peptide were measured in the basal and glucose-stimulated state in middle-age males. Normals were compared with individuals with mild to moderate glucose intolerance. Ths results demonstrate the value of C-peptide measurements in the assessment of "true" insulin secretion and suggest that a reduced hepatic insulin extraction is a feature of the glucose intolerant state.