From the Guidelines
Insulinoma symptoms primarily result from hypoglycemia due to excessive insulin secretion by this pancreatic tumor, and the classic presentation includes Whipple's triad: hypoglycemic symptoms, low blood glucose levels, and relief of symptoms after glucose administration. The symptoms of insulinoma can be divided into two main categories: neuroglycopenic and autonomic symptoms. Neuroglycopenic symptoms occur due to the lack of glucose in the brain and include confusion, unusual behavior, visual disturbances, weakness, fatigue, seizures, and even loss of consciousness or coma 1. Autonomic symptoms, on the other hand, occur as the body responds to low blood sugar, including sweating, trembling, heart palpitations, anxiety, and hunger.
- These symptoms typically appear during fasting or exercise when blood glucose naturally decreases, but can sometimes occur after meals.
- A distinctive feature of insulinoma is weight gain, as patients may eat frequently to avoid hypoglycemic episodes.
- Symptoms can be intermittent and vague, often leading to misdiagnosis as psychiatric, neurological, or cardiac disorders. The severity and frequency of symptoms depend on insulin secretion patterns, with some patients experiencing mild occasional symptoms while others have frequent severe episodes requiring emergency care 1. Morning headaches and nightmares may occur due to nocturnal hypoglycemia. Prompt evaluation is essential as prolonged or severe hypoglycemic episodes can cause permanent neurological damage.
- It is also important to note that insulinomas can be localized by injecting calcium into selective pancreatic arteries and measuring the insulin levels in the right or left hepatic vein (Imamura-Doppman procedure) 1.
- Serum insulin, proinsulin, and C peptide should be tested to confirm the diagnosis of insulinoma, and a 48- to 72-hour observed or inpatient observed fast may also be helpful in uncertain cases 1.
From the Research
Symptoms of Insulinoma
The symptoms of insulinoma are primarily caused by hypoglycemia, which leads to neuroglycopenia and catecholamine response 2. Some of the key symptoms and characteristics include:
- Hypoglycemia with blood glucose levels less than 40 mg/dl (less than 2.2 mmol/l) 2
- Concomitant insulin levels greater than or equal to 6 IU/ml (greater than or equal to 43 pmol/l) 2
- Concomitant C-peptide levels greater than or equal to 0.2 pmol/l 2
- Neuroglycopenic and hypoglycemic symptoms, such as confusion, shakiness, and loss of consciousness 3
- Catecholamine response, which can cause symptoms such as palpitations, sweating, and anxiety 2
Diagnosis and Management
The diagnosis of insulinoma is typically confirmed by a supervised fast, and early detection is important 4. The management of insulinoma usually involves surgical excision of the tumor, which can be curative in most cases 2, 4. In some cases, medical therapy with somatostatin analogues, such as octreotide or lanreotide, may be used to control hypoglycemia 5, 6.
Complications and Treatment
In some cases, insulinoma can be associated with other conditions, such as multiple endocrine neoplasia type-1 syndrome 4 or pheochromocytoma 6. The treatment of insulinoma may involve a multidisciplinary approach, including surgery, medical therapy, and lifestyle modifications 2, 4, 6, 3.