Arnqvist H J, Halban P A, Mathiesen U L, Zahnd G, von Schenck H
Department of Internal Medicine, Faculty of Health Sciences, Linköping University, Sweden.
J Intern Med. 1993 Oct;234(4):421-7. doi: 10.1111/j.1365-2796.1993.tb00766.x.
We describe a 48-year-old woman with recurrent severe hypoglycaemia apparently caused by a paraprotein with insulin-binding capacity. Very high fasting values were found for serum insulin (170 and > 250 mU l-1) as well as for proinsulin 125 pmol l-1 and an insulinoma was suspected. Hypoglycaemia developed after an oral glucose tolerance (OGTT) test but not during fasting for 48 h. Free insulin and C-peptide were normal during OGTT whereas serum insulin was very high. 125I-insulin binding to serum, determined with a polyethylene glycol (PEG) precipitation method was high (40%), and equally high after addition of 1.7 x 10(-5) mol l-1 cold insulin to estimate non-specific binding. By adding very high concentrations of cold insulin, displacement of 125I-insulin bound to serum was found (50% displacement at 4 x 10(-5) mol l-1). No immunoglobulin G (IgG) insulin antibodies were detected by radioimmunoelectrophoresis. On agarose electrophoresis a small paraprotein (4 g l-1) in the gamma-globulin fraction was detected. 125I-insulin binding to this paraprotein was demonstrated. We conclude that if insulin autoantibodies are suspected as a cause of hypoglycaemia screening for insulin antibodies should always be done with a PEG-precipitation method.
我们描述了一名48岁的女性，她反复出现严重低血糖，显然是由具有胰岛素结合能力的副蛋白引起的。血清胰岛素空腹值极高（170和>250 mU l-1），胰岛素原125 pmol l-1，怀疑患有胰岛素瘤。口服葡萄糖耐量试验（OGTT）后出现低血糖，但禁食48小时期间未出现。OGTT期间游离胰岛素和C肽正常，而血清胰岛素非常高。用聚乙二醇（PEG）沉淀法测定的125I-胰岛素与血清的结合率很高（40%），加入1.7 x 10(-5) mol l-1冷胰岛素以估计非特异性结合后同样很高。通过加入非常高浓度的冷胰岛素，发现与血清结合的125I-胰岛素发生了位移（在4 x 10(-5) mol l-1时50%的位移）。放射免疫电泳未检测到免疫球蛋白G（IgG）胰岛素抗体。在琼脂糖电泳中，在γ球蛋白部分检测到一种小的副蛋白（4 g l-1）。证实了125I-胰岛素与这种副蛋白的结合。我们得出结论，如果怀疑胰岛素自身抗体是低血糖的原因，应始终用PEG沉淀法进行胰岛素抗体筛查。
