业已证明,前胰岛素的A链和B链为一个由30～35个氨基酸组成的肽连接。当中氨基酸的数目因动物种类的不同而异。在人类此种多肽由31个氨基酸组成,其排列次序已明确,并被命名为“连接肽”或“C肽”。根据放射免疫测定,健康入空腹时血清C肽的浓度为1～2毫微克/毫升。血清C肽的放射免疫测定对下列情况的诊断均有帮助: It has been demonstrated that the A and B chains of proinsulin are linked by a peptide consisting of 30 to 35 amino acids. The number of amino acids varies among animal species. In humans, this polypeptide consists of 31 amino acids and the order of its arrangement has been established and is named “linker peptide” or “C peptide.” According to radioimmunoassay, serum C-peptide concentration of 1 to 2 ng / mL at healthy fasting time. Radioimmunoassay of serum C-peptide helps in the diagnosis of