Also known as pancreatic beta cell tumor, it is an adenoma or carcinoma formed by pancreatic beta cells with secretory function. It commonly occurs between the ages of 20 and 50, is usually solitary, and 90% are benign. Occasionally, it may be part of type I multiple endocrine neoplasia.

bubble_chart Diagnosis

1. Medical history, symptoms, and signs

The onset is slow, and a few cases may take a long time to be diagnosed. Long-term misdiagnosis can cause permanent brain damage. Clinical manifestations include:

(1) Whipple’s triad: ① Hypoglycemic symptoms occur after hunger or exercise;

② Blood glucose during episodes is <2.8 mmol/L (50 mg/dl);

③ Immediate relief after glucose injection.

(2) Hypoglycemic episodes often become more frequent as the disease progresses, with prolonged duration and worsening severity, and may even be induced postprandially. Most cases are accompanied by gradual obesity and declines in memory and responsiveness.

2. Auxiliary examinations:

(1) Blood glucose during episodes is <2.8 mmol/L (50 mg/dl).

(2) Serum insulin and C-peptide: Plasma insulin and C-peptide levels are elevated during hypoglycemia, with an insulin index (insulin/glucose) >0.3. A value >1.0 confirms the diagnosis. Fasting plasma insulin >200 uU/ml also confirms the diagnosis.

(3) Oral glucose tolerance test: Typically shows a flat curve, with some cases exhibiting impaired glucose tolerance, and a few showing early hypoglycemia or normal glucose tolerance curves.

(4) Fasting test: A positive result aids diagnosis. The test can only be performed if fasting blood glucose is >2.8 mmol/L. Over 90% of cases will develop hypoglycemia after 24–36 hours of fasting. A few cases require fasting for 48–72 hours, with added exercise 2 hours before ending the fast to induce hypoglycemia. If hypoglycemia is not induced after 72 hours of fasting, the disease can be ruled out. (5) Localization diagnosis: Pancreatic B-ultrasound, CT, pancreatic pulse contrast imaging, and catheter insertion into the hepatic portal vein to the splenic vein for blood sampling to measure insulin levels are helpful for localization diagnosis.

It should be distinguished from epilepsy, cerebrovascular accidents, hysteria, schizophrenia, and hypoglycemia caused by other diseases.

bubble_chart Treatment Measures

1. Surgical removal of the tumor. If the tumor cannot be located during the operation, subtotal pancreatectomy may be performed.

2. For patients with surgical contraindications, those who refuse surgery, or those with unresolved or recurrent symptoms after surgery, diazoxide can be administered at 100–200 mg/day, divided into 2–3 doses. Concurrent use of diuretics can prevent water retention side effects. Phenytoin and propranolol also have some inhibitory effects on insulin secretion. Adrenocortical hormones may also alleviate symptoms.

3. For unresectable or metastatic islet cell carcinoma, streptozotocin can be used, with 50% of patients achieving symptom relief or prolonged survival. During drug therapy, increasing meal frequency and consuming more sugar- and fat-rich foods is recommended. Adrenocortical hormones may also be added as needed to prevent hypoglycemic episodes.