What are the symptoms of an insulinoma (insulin-producing tumor)?

From the Guidelines

Insulinoma symptoms primarily result from hypoglycemia (low blood sugar) caused by the tumor's excessive insulin production, and common symptoms include confusion, visual disturbances, unusual behavior, palpitations, tremors, sweating, weakness, hunger, and anxiety, as noted in the guidelines for the management of gastroenteropancreatic neuroendocrine tumours 1. These symptoms typically occur during fasting or exercise when blood sugar naturally decreases. A distinctive feature of insulinoma is "Whipple's triad": hypoglycemia symptoms, documented low blood glucose levels (below 50 mg/dL), and relief of symptoms after glucose administration. Some patients may experience severe manifestations like seizures, loss of consciousness, or even coma if hypoglycemia is profound. Weight gain is also common as patients often eat frequently to prevent hypoglycemic episodes. Symptoms may develop gradually and be misdiagnosed as psychiatric, neurological, or cardiac disorders. The hypoglycemic episodes can occur at any time but are most common in the early morning or when meals are delayed. Key diagnostic criteria include an insulin level greater than 3 mcIU/mL, C peptide concentrations of at least 0.6 ng/mL, and proinsulin levels of greater than or equal to 5 pmol/L when fasting blood glucose is less than 55 mg/dL, as outlined in the neuroendocrine tumors guidelines 1. If you experience recurrent hypoglycemic symptoms, especially when fasting, seek medical attention promptly as early diagnosis of insulinoma leads to better treatment outcomes. Some important points to consider in the diagnosis and management of insulinoma include:

• The use of multiphasic CT or MRI scans to rule out metastatic disease 1
• The potential for somatostatin analogues to worsen hypoglycemia in some cases, and the need for careful monitoring when using these agents 1
• The importance of considering insulinoma in the differential diagnosis of patients presenting with recurrent hypoglycemic symptoms, especially in the context of fasting or exercise 1

From the Research

Symptoms of Insulinoma

The symptoms of an insulinoma, a rare neuroendocrine tumor of the pancreas, can be diverse and affect various systems of the body. Some common symptoms include:

• Autonomic symptoms:
  • Diaphoresis (sweating) 2, 3
  • Tremor 2, 3
  • Palpitations 2, 3
  • Tachycardia 4, 3
• Neuroglycopenic symptoms:
  • Confusion 4, 2, 5, 3, 6
  • Behavioral changes 2, 5
  • Personality changes 4, 2
  • Visual disturbances 4, 2, 3
  • Seizures 4, 2, 5, 6
  • Coma 2, 3
• Other symptoms:
  • Weakness 4, 3
  • Fatigue 2, 5
  • Hunger 4, 5
  • Headache 4
  • Dizziness 4, 5
  • Disorientation 4
  • Unconsciousness 4
  • Syncope 3

Unusual Presentations

Insulinomas can sometimes present with unusual symptoms, making diagnosis challenging. These unusual presentations can include:

• Seizures 5, 6
• Absence seizures 6
• Complex partial seizures 4
• Neurologic or psychiatric symptoms, such as disorientation, personality changes, amnesia, irritability, and bizarre behavior 4