UNASSIGNED: The most common cause of organic fasting @entity4053 in adults is the presence of an insulin-producing @entity36915 , but when high insulin levels are not found, the differential diagnosis is challenging. Misdiagnosis can lead to an unnecessary pancreatectomy. Insulin concentrations may be low in some cases despite a clinical history suggestive of @entity9608 . In these cases, a proinsulinoma should be suspected, although the rarity of this condition requires an extensive workup before reaching a final diagnosis. We describe an unusual case of a 38-year-old @entity1 with a severe @entity751 due to a @entity2690 -secreting @entity36915 . Insulin was measured by the specific assay and suppressed under the lower detection limit during fasting @entity4053 . Serum @entity2690 and C-peptide levels were abnormally elevated, and further tests revealed an islet cell @entity5 . The @entity5 was surgically removed, relieving the fasting @entity4053 . Histopathological study showed a conventional well-differentiated @entity5 with high immunoreactivity against @entity2690 and with lesser intensity against insulin. Interestingly, GS-9A8 antibody clone used for immunostaining @entity2690 did not cross-react with @entity1 insulin or C-peptide, providing an unbiased picture of @entity2690 secretion. The resolution of symptoms, the fall of @entity2690 concentrations after @entity5 removal and the histopathology study confirmed the diagnosis of proinsulinoma.

XXXX without Hyperinsulinemia. A Diagnostic Challenge.

@entity1 :: ('9606', 'Species') :: ['human', 'man'] @entity9608 :: ('MESH:D007340', 'Disease') :: ['insulinoma'] @entity5 :: ('MESH:D009369', 'Disease') :: ['tumor', 'neuroendocrine tumor'] @entity2690 :: ('3630', 'Gene') :: ['proinsulin'] @entity4053 :: ('MESH:D007003', 'Disease') :: ['hypoglycemia'] @entity751 :: ('MESH:D013577', 'Disease') :: ['hypoglycemic syndrome'] @entity36915 :: ('MESH:C538110', 'Disease') :: ['pancreatic adenoma']
@entity751 :: (MESH:D013577,Disease) :: ['Hypoglycemic Syndrome']
