title: Insulinoma with low circulating insulin levels: the diagnostic value of proinsulin measurements.
abstract: Hypoglycemia coexisting with very low plasma immunoreactive insulin concentrations was found in a 78-year-old woman with an insulinoma. However, the absolute proinsulin levels during hypoglycemia were elevated (0.9 to 1.4 ng/ml), accounting for 66.5% of the total circulating immunoreactive insulinlike material. The raised serum proinsulin concentrations together with an abnormal proinsulin:insulin ratio proved to be of critical importance in establishing the diagnosis of an islet-cell tumor in this patient.
mesh_terms: D007516:Adenoma, Islet Cell / Q000097:blood* / Q000175:diagnosis / Q000601:surgery; D000368:Aged; D000941:Antigens / Q000032:analysis; D001786:Blood Glucose / Q000032:analysis; D002850:Chromatography, Gel; D005215:Fasting; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007003:Hypoglycemia / Q000097:blood; D007328:Insulin / Q000097:blood* / Q000276:immunology; D010190:Pancreatic Neoplasms / Q000097:blood* / Q000175:diagnosis / Q000601:surgery; D011384:Proinsulin / Q000097:blood*; D013997:Time Factors
chemical_list: D000941:Antigens; D001786:Blood Glucose; D007328:Insulin; D011384:Proinsulin