Insulinoma

Evaluate patients with Whipple triad or recurrent fasting neuroglycopenia by drawing plasma glucose, insulin, C-peptide, proinsulin, beta-hydroxybutyrate, and a sulfonylurea/meglitinide screen during spontaneous hypoglycemia. Give glucagon 1 mg IV after the specimen is collected; a plasma glucose rise greater than 25 mg/dL supports hyperinsulinemic hypoglycemia. PubMedPubMedHypoglycemia - Endotext - NCBI Bookshelf - NIH

At plasma glucose below 55 mg/dL, insulin of at least 3 µU/mL, C-peptide of at least 0.6 ng/mL, proinsulin of at least 5 pmol/L, beta-hydroxybutyrate no more than 2.7 mmol/L, and a negative sulfonylurea screen support endogenous hyperinsulinemic hypoglycemia. These results establish the physiologic syndrome requiring localization; they do not by themselves prove a pancreatic insulinoma. PubMed+1PubMedInsulinoma - StatPearls - NCBI BookshelfPubMedInsulinoma—Accurate Preoperative Localization Is the Key to Management: An Initial Experience

A low C-peptide in the setting of detectable insulin redirects the evaluation toward exogenous insulin exposure. Detectable sulfonylurea or meglitinide redirects management toward secretagogue-associated hypoglycemia rather than tumor localization. Suppressed ketogenesis, reflected by beta-hydroxybutyrate below 2.7 mmol/L, is a key discriminator of insulin-mediated hypoglycemia. PubMed+1PubMedNon-Diabetic Hypoglycemia - StatPearls - NCBI BookshelfPubMedHypoglycemia - Endotext - NCBI Bookshelf - NIH

Perform a monitored fast when the clinical history is compelling but an episode has not been captured. Permit noncaloric, caffeine-free beverages; measure glucose, insulin, and C-peptide at baseline and every 4 to 6 hours. Once plasma glucose falls below 60 mg/dL, increase sampling to every 1 to 2 hours with close observation. PubMedPubMedHypoglycemia - Endotext - NCBI Bookshelf - NIH

Terminate the fast when neuroglycopenic symptoms occur with plasma glucose below 45 mg/dL; the Endocrine Society threshold cited in Endotext is below 55 mg/dL. At termination, obtain glucose, insulin, C-peptide, proinsulin, beta-hydroxybutyrate, and an oral insulin secretagogue screen before treating hypoglycemia. PubMedPubMedHypoglycemia - Endotext - NCBI Bookshelf - NIH

Most patients with insulinoma develop symptomatic hypoglycemia before the full 72 hours: approximately one-third by 12 hours, 80% by 24 hours, and 90% by 48 hours. A negative or non-diagnostic fast should prompt reconsideration of the event phenotype, particularly postprandial rather than fasting hypoglycemia, before pursuing invasive localization. PubMedPubMedInsulinoma—Accurate Preoperative Localization Is the Key to Management: An Initial Experience

Begin with contrast-enhanced CT to localize the pancreatic lesion and determine whether metastatic disease is present. For an apparently indolent localized lesion, use EUS or MRI as the next anatomic study when CT is negative or insufficient for procedural planning. Approximately 30% of insulinomas are smaller than 1 cm, making localization technically challenging. PubMed+1PubMedInsulinoma - Endotext - NCBI BookshelfPubMedApproach to the Patient: Insulinoma - PMC

When CT, MRI, and EUS do not identify a lesion in biochemically proven endogenous hyperinsulinism, obtain GLP-1 receptor PET/CT or PET/MRI for occult, localized insulinoma. This modality is described as highly sensitive for indolent localized lesions and can avoid blind pancreatic resection. PubMed+1PubMedInsulinoma - Endotext - NCBI BookshelfPubMedApproach to the Patient: Insulinoma - PMC

Somatostatin receptor imaging has a different role. Gallium-68 somatostatin analogue PET/CT is the most sensitive modality for pNET and NET localization broadly and is recommended for surgical candidates and advanced disease staging, but conventional somatostatin receptor scintigraphy frequently misses insulinomas because of lower receptor density. A negative somatostatin receptor study therefore should not end the localization workup for a suspected small localized insulinoma. PubMed+1PubMedENETS Consensus Guidelines for the Management of Patients with Digestive Neuroendocrine Neoplasms: Functional Pancreatic Endocrine Tumor SyndromesPubMedConsensus guidelines update for the management of functional p-NETs (F-p-NETs) and non-functional p-NETs (NF-p-NETs)

If noninvasive studies remain negative despite unequivocal endogenous hyperinsulinemic hypoglycemia, refer to a high-volume pancreatic NET center for specialized localization and operative planning. Intraoperative palpation and intraoperative ultrasonography are important adjuncts, particularly when preoperative imaging is incomplete. ScienceDirect+1ScienceDirectThe surgical management of insulinomas in children - ScienceDirectPubMedChanges in diagnosis and operative treatment of insulinoma over two decades - PMC

Patients with frequent fasting hypoglycemia, impaired awareness, seizures, or altered consciousness need immediate carbohydrate rescue and monitored glucose support while the critical sample and localization pathway are completed. During operative care, use perioperative glucose monitoring to detect and prevent hypoglycemia. ScienceDirect+1ScienceDirectInsulin Blood Level - an overview | ScienceDirect TopicsPubMedENETS Consensus Guidelines for the Standards of Care in Neuroendocrine Tumors: Pre- and Perioperative Therapy in Patients with Neuroendocrine Tumors

For persistent hypoglycemia when surgery is delayed, contraindicated, or noncurative, use dietary measures and medical therapy to reduce hypoglycemia burden. Somatostatin receptor ligands may be used for hypoglycemia control, but therapeutic selection should account for receptor imaging and clinical response rather than presuming uniform benefit. PubMed+1PubMedApproach to the Patient: Insulinoma - PMCWileyManaging Hypoglycaemia in Patients With Insulinoma—A Tertiary Centre Experience and Review of the Literature - Howarth - 2025 - Clinical Endocrinology - Wiley Online Library

Continuous glucose monitoring can provide practical surveillance in patients with recurrent or poorly perceived hypoglycemia, particularly during medical bridging or advanced disease management; it complements but does not replace laboratory confirmation of endogenous hyperinsulinism. WileyWileyManaging Hypoglycaemia in Patients With Insulinoma—A Tertiary Centre Experience and Review of the Literature - Howarth - 2025 - Clinical Endocrinology - Wiley Online Library

Offer surgery for a solitary localized insulinoma after biochemical confirmation and conclusive localization. Surgical excision is the treatment of choice and is generally curative for localized pancreatic insulinoma. Select enucleation when lesion location permits safe parenchymal preservation; use partial pancreatectomy when anatomy precludes enucleation or requires formal resection. PubMed+2PubMedInsulinoma - Endotext - NCBI BookshelfPubMedChanges in diagnosis and operative treatment of insulinoma over two decades - PMCPubMedApproach to the Patient: Insulinoma - PMC

Use preoperative lesion location to choose minimally invasive, robot-assisted, or open surgery and to plan enucleation versus partial pancreatectomy. Intraoperative ultrasound and palpation can confirm lesion position and relationship to the pancreatic duct, particularly for small or occult tumors. PubMed+1PubMedInsulinoma - Endotext - NCBI BookshelfPubMedChanges in diagnosis and operative treatment of insulinoma over two decades - PMC

Counsel patients about pancreatic morbidity when selecting the operative approach. In one three-decade surgical series, pancreatic fistula occurred in 44%, severe complications in 30%, overall morbidity in 72%, and mortality in 6%; these outcomes reflect a reported surgical cohort and reinforce the importance of experienced multidisciplinary pancreatic surgery. ScienceDirectScienceDirectSurgical management of insulinoma over three decades

Pathology should document neuroendocrine differentiation with chromogranin A and synaptophysin immunostaining plus insulin staining; determine mitotic index and Ki-67 for grading and apply current WHO TNM classification. PubMed+1PubMedENETS Consensus Guidelines for the Management of Patients with Digestive Neuroendocrine Neoplasms: Functional Pancreatic Endocrine Tumor SyndromesPubMedInsulinoma - StatPearls - NCBI Bookshelf

Assess resectability and metastatic burden with cross-sectional and receptor-based imaging before selecting therapy. For aggressive malignant disease, management may combine debulking procedures, somatostatin receptor ligand therapy, everolimus, and peptide receptor radionuclide therapy; selection depends on disease extent, clinical hypoglycemia, and somatostatin receptor expression. PubMedPubMedApproach to the Patient: Insulinoma - PMC

Consider peptide receptor radionuclide therapy in metastatic or inoperable disease, particularly when somatostatin receptor expression is demonstrated. A contemporary review describes PRRT as a first-line approach alongside somatostatin analogues for metastatic or inoperable insulinoma because it can improve progression-free survival and provide durable improvement in hypoglycemia; the strength of evidence is limited by the rarity of the disease. WileyWileyManaging Hypoglycaemia in Patients With Insulinoma—A Tertiary Centre Experience and Review of the Literature - Howarth - 2025 - Clinical Endocrinology - Wiley Online Library

Everolimus has produced rapid glycemic responses in metastatic insulinoma, including plasma glucose normalization within 14 days in a small report, and should be considered in refractory hypoglycemia when tumor-directed systemic therapy is needed. Sirolimus improved glycemic control in four infants with diffuse hyperinsulinemic hypoglycemia unresponsive to diazoxide and octreotide, but that pediatric experience should not be extrapolated as standard adult insulinoma therapy. NEJMNEJMSirolimus Therapy in Infants with Severe Hyperinsulinemic Hypoglycemia | New England Journal of Medicine

For liver-dominant metastatic disease with refractory hypoglycemia, liver-directed therapy may be considered within a NET multidisciplinary program. A reported case of unresectable malignant insulinoma with liver metastases had hypoglycemia resolution after four courses of lutetium-177 dotatate PRRT, following incomplete response to long-acting octreotide and everolimus. Wolters KluwerWolters KluwerAdvanced Peptide Receptor Radionuclide Therapy to... : Journal of Medical Sciences