Diagnosis of insulinoma in a patient with hypoglycemia without obvious hyperinsulinemia

Usefulness of hemoglobin A1c and glycated albumin measurements for insulinoma screening: an observational case-control study

Background

Insulinoma represents hypoglycemia as a predominant symptom; the autonomic symptoms may be resolved by chronically recurrent hypoglycemia resulting in the persistence of non-specific symptoms alone. Therefore, it has been estimated that there are many patients in whom the disease takes longer to diagnose and has remained undiagnosed. Although some parameters exist for the definitive diagnosis of the disease, there are currently no indices for early screening. Indices of glycemic control, hemoglobin A1c (HbA1c), and glycated albumin (GA) may be useful for the screening of patients with insulinoma having chronic hypoglycemia because the values become low in such a condition. Because there are no articles that have reported the point, we examine the effective cutoff values of HbA1c and GA for the diagnosis of insulinoma in the present study.

Methods

In a multicenter cross-sectional study, 31 patients with insulinoma were included for comparison with 120 control subjects with normal glucose tolerance based on 75 g oral glucose tolerance tests whose characteristics were matched to the patients. The primary outcomes were optimal cutoff values of HbA1c and GA for the screening of insulinoma.

Results

HbA1c was significantly lower in the insulinoma group at 4.7 ± 0.4% compared to the healthy control group at 5.7 ± 0.3% (p < 0.001), and GA was significantly lower in the insulinoma group at 11.6 ± 1.8% compared to the healthy control group at 14.5 ± 1.0% (p < 0.001). According to a receiver operating characteristic (ROC) analysis, optimal cutoff values of HbA1c and GA for the diagnosis of insulinoma were 5.0 and 12.4%, respectively. Area under the curve values of HbA1c and GA were 0.970 and 0.929, respectively, showing no significant difference (p = 0.399).

Conclusions

In the present study, HbA1c and GA values in patients with insulinoma were significantly lower compared to the healthy controls, and effective cutoff values for screening were shown in the diagnosis of insulinoma for the first time. HbA1c and GA can be useful indices for insulinoma screening. Because malignant insulinoma have a similar diagnostic process to that of benign insulinoma, these could be useful for malignant insulinoma.

Hypoglycemia identified by a continuous glucose monitoring system in a second-trimester pregnant woman with insulinoma: a case report

BACKGROUND

Insulinoma associated with pregnancy is a very rare condition and can be difficult to diagnose. Here, we present an interesting case of insulinoma occurring during pregnancy with special attention paid to the use of a continuous glucose monitoring system to detect hypoglycemia.

CASE PRESENTATION

A 36-year-old white woman in the second trimester of pregnancy presented with recurrent episodes of hypoglycemia associated with neuroglycopenic symptoms. The use of a continuous glucose monitoring system confirmed hypoglycemia. Serum insulin, C-peptide, and proinsulin values confirmed endogenous hyperinsulinism. A tumor mass was localized at the tail of her pancreas by endoscopic ultrasound and confirmed by magnetic resonance imaging. Surgery performed at 21 weeks of gestation by distal pancreatectomy confirmed the presence of a 15 mm diameter endocrine tumor at the tail of her pancreas and led to a cure.

CONCLUSIONS

Hypoglycemia during pregnancy could be due to insulinoma. Use of a continuous glucose monitoring system could help to detect hypoglycemia in these patients.

[Endogenous hyperinsulinism: two diagnostic challenges]

Hypoglycemia in apparently healthy adults is a rare finding in clinical practice requiring a thorough investigation of the cause. During the investigation, identification of hypoglycemia associated with inappropriately high levels of insulin and C-peptide should prompt the exclusion of rare causes of hypoglycemia, including pancreatic islet-cells disease and autoimmune hypoglycemia. In this paper, we describe two cases of hypoglycemia associated with endogenous hyperinsulinism, whose causes are uncommon in clinical practice, and review important aspects of the diagnosis and treatment of hyperinsulinemic hypoglycemia.

Insulinoma and anaesthetic implications

Insulinoma is a rare neuroendocrine tumour of the pancreas , which is usually small, solitary and benign. It may be part of the multiple endocrine neoplasia type 1 syndrome. It is diagnosed by clinical, biochemical and imaging modalities. Hypoglycaemic symptoms can be medically controlled by diazoxide or somatostatin analogues. Localisation of the tumour is a challenge to clinicians. Surgical resection is the curative treatment with a high success rate. Intraoperatively, ultrasound and surgical palpation help to confirm the site of tumour. Intraoperatively, maintenance of optimum glucose levels is of main concern because there may be severe hypoglycemia while handling the tumour, symptoms of which remain masked under general anaesthesia. Glucose infusion and frequent plasma glucose monitoring to maintain plasma glucose level more than 60 mg/dL is found to be helpful. We performed a systematic search in PubMed, Cochrane Library and also in Google. We used the following text words for our search: Insulinoma, neuro-endocrine tumors, multiple endocrine neoplasia, hypoglycemia, anaesthetic management of insulinoma, glucose management. In this article, we review the incidence and epidemiology of insulinoma, its clinical features, diagnosis, localisation and treatment, with special emphasis on anaesthetic management.

Beta-cell adenomas without hyperinsulinemia with use of highly specific insulin radioimmunoassays: case report and review of literature

OBJECTIVE

To report a case of a proinsulin-secreting islet cell adenoma in which the diagnosis was obscured by an ultraspecific insulin assay.

METHODS

We describe the case of a 46-year-old woman, who presented with fasting hypoglycemia and appropriately low insulin values.

RESULTS

A prolonged supervised fast produced symptomatic hypoglycemia (20 mg/dL) after only 7 hours. During the entire fasting test, highly specific insulin remained at <3 mIU/L, with a median value (and interquartile range) of 0.9 (0.8 to 2.3) mIU/L, when the glucose concentration was <50 mg/dL. The serum C-peptide level remained high normal (mean +/- SD, 2.7 +/- 0.6 ng/mL; normal fasting levels, 0.8 to 3.9), and no evidence of sulfonylurea use was detected in the patient's urine. Circulating proinsulin levels were persistently high (>200 pmol/L in all determinations when hypoglycemia was present; expected value, <5 pmol/L). Magnetic resonance imaging and endoscopic ultrasonography confirmed the presence of a 2.5-cm tumor in the head of the pancreas. A proinsulin-secreting islet cell tumor was diagnosed. Surgical resection of the tumor was successfully accomplished, but diabetes mellitus developed 4 months postoperatively.

CONCLUSION

The diagnosis of a hypoglycemia-producing pancreatic adenoma can be missed when an ultraspecific insulin assay is used. The direct measurement of proinsulin established the diagnosis in this case.