2.1.2. Quantitative and qualitative alterations in insulin secretion
In type 2 diabetes, a decrease in basal and stimulated insulin plasma levels has been reported, whatever the BMI [18]. Specific immunoradiometric assay has distinguished true insulin deficiency, masked in type 2 diabetes by an excess in circulating prohormones: pro-insulin, split 32-33 and 64-65 proinsulin, accounting for more than 40% of the circulating peptides (5% in non-diabetics) [19]. This excess in proinsulin is not a consequence of hyperstimulation of the β-cell, as it is
absent from the states of secondary hyperinsulinism, such as obesity and liver diseases.